Volume 26 (1873) (431 pages)

March 15, 1873.] MINING AND SCIENTIFIC PRESS. 163 I ECHANICAL sP RoaRESS The Band Saw and Ban Sawing. (Continued.] In continuing our extract from the very interesting article on ‘‘ Band Saws’’ from Riehards’ treatise on Wood-Working, which we noticed last week, we now come to the subject. Band Saw Blades. ‘Tho bladea for hand sawsshnuld have what is technically known as ain 4 temper, or if different, a shade above in hardness. If much harder, they are liahle to fracture from irregular tension, or concussion of any kind, expensive to aharpen, and difficult to set without breaking the tceth. Rendered sefter than this, thoy are simply worthless, and should have no market value. Theamonnt or degree of teinper in a saw blade is quite an ohscure matter, one that eannot be determine 1 to any certainty by observation, and hardly hy experimont, fer although a blado ie properly tempered throughout nine-tenths of ita length, anal certain spota are drawn, agis often thecase in grinding, or glazing, the hlade is more worthless than if eoft throughout. The purchasers of sawa are, therefore, incapable of testing the quality of the eawe, and the time of buying muet depend upon the geod faith of the manufacturers, who usually, and very properly too, are understood as guaranteeing the saw tn be of even and good temper, and of fine ateel. Tho working quality, and indeed the whole value of the caw, isin great measure dependent upon tne eare and skill of the saw maker, of which there exist no evidence, or at leaet un ise facie evidence in the appearance of the blades when finiched. In celecting hand-saw blades a goed plan ie to roll the ends closely, and ace if tbey will epring back te their first pesition. The texture of the eteel can be examined by breaking ashort piece from the end, the differance hetween coarse granular fracture, and fine lvely-looking steel heing familiar matter to most mechanics. To determine the etraightness of the blade if not joined, unroll it on the floor, and by ‘‘sighting it,”’ irregularities are eacily detected. Another mnst important matter ie an exact parallel as to width; the slightest variation in this regard becomes a aerioua objection to “the operation of 2 saw, preducing ecratches on the work, irregular action of the teeth, and consequent irregular tension of the blade through its cutting at intervale ouly. Any variation of width between the two ende of a blade can be easily detected by lapping them, and miecing tha points of the teeth ona plane anrface, which will ahow on the backe any differance of width, however little it may 0. The pitch, depth, and form of teeth for band sawa, is a matter abont which there is snch a diversity of npinion, that the only safe inference ie, that it is either a matter of no great importance, or else not understood. Wealludeof course to eaws for epecial purposea; for varioue modificatione of the teeth are needed in different cases, and unfortunately the condition that has most to do with the change is continually varying, that is, the depth of the lumber. In considering caw teeth, we have fira', pitch (distance hetween teeth); the inclination on front aud back of the tooth (cutting angle); the form of the gullet, as it is termed, for holding the dust; the width of the haae of the tooth, eo as to give eufficient stiffness to retain the “set”; and the kind of set given to the teeth. It would be supposed that the experience of operating other saws would furnish all that could be learned of baud saws, hut thie doee not seem by any means to be the case. The thinneee of the hlades calls for every minute condition that will tend to keen them true, and toruninline. With a thick circular, or reciprocating aaw, the caeeis different; it can he forced to its work, and made to operate without that nice regard to the condition and form of the teeth that must he ohserved in band eawing. For aoft wood, a pitch equal to one-half, and a depth equal to one-fifth of the width of the blade, ie as near a general rule as can at this time be euggested. For hard wood a closer pitch of one-third the width is. better. The gullet or throat under the tooth should in all caaes be circular; not only to guard against breaking or checking in the cornere, but to revent the dust from lodging; ae with an acute angle it can be carried in quantities on to the wheels, For the front inclination of the teeth, it ehould be eufficient, eo that when. the sawia aharp there will be no back thrust on bladea; a thing that must in each case be determined by the observation of the operator, and the character of the timber to be ont. . In the matter of setting, it must be determined by the thicknese of the blade and character of the wood. In sawing pine, or other soft woods, the teeth can be bent from the base, and will retain their set; but in hard wood or knote this kind of setting does not last long, but eoon “‘ cumee ont,’’ to uee a lumberman’s expression. Upsetting the teeth ie impracticable with thin eaws, or at least ie very difficult, unieaa the plates are No. 14 or thicker. The temper besides is, or ought to be, too high in band sawe for upsetting. The best plan of seting developed in the writer’s experience, in band eawing, is a 5 acy abrupt bend on the bottom of the tooth by ‘‘sharp hlows’’ from a light hammer—setting the steel, n3 it were, off to one side and raising a kink of scraping edge on the entting side of the tooth. It is easy to get a regular or smeoth set in this manner, and it requirs no special skill to perform it; it is besides sooner done, no gauge heing required. Thosaw is passed over an anvil, with is top bevelled to a proper angle, tho hotton: cdge of the toeth projecting over tho bevel, from the sixtcenth to one-eight of an inch, according to the amount of set required. ; These remarks upon toeth relato to saws intended for power or positive speed. For screll sawing or plain had slitting it is presumed that no information of any interest could he given, and that none is needed. {To be Continued.] Conveying Air Through Pipes. A Supposed Valuable Invenlicn Explained Away. We sometime since gave a description of a new device for conveying compressed air through pipes for motive pnwer, wherehy it was suppesed the friction of the air upon the walls of the tubs was done away with. The invention may be auhstantially described ns followe :— Jf, ina pipe nf twelve inches diameter we make at intervals necks of ten inches in diameter, we have an annular space one inch deep around the inner circumference of the pipe. The theery is that the air contaiued in this epace does not meve, but remains at rest, and thue presents an air eurface te the meving mase of air ten inehes in diameter which flows threugh the necke. As the friction ofair on air is leos than that ef air on iron, he expects to convey power in the ehape of compressed air with almost no loss frem friction. The invention is claimed by a Mr. Spear, of Bostou, and the marvel wasendorsed hy Willium A. Goodwin, ‘‘city engineer of Portland, and for aome years gevernment lighthouse engineer,’’ who had given the invention a practical trial, and, as he supposed a thorough teet as follows: He set a pressure gauge on a reservoir which received cempressed eir, and when a pressure of 40 lbs. was indicated, opened an orifice in the reservoir so large ae to exhaust the effect of the compressor as faet as delivered. The compreesor is now working into the reservoir, the orifice blowing off and the gauge stands at 40. Suppose the orifice to be one inoh in diameter. Now attach to the same a pipe of one inch in calihre, eay 100 feet long. Ata point near the onter end of this pipe seta pressure gauge, and the preesure with the pipe wide open, will he found to be something less than 40 Ibs. The element of friction has been developed in the pipe. Now take an additional pipe 124 inches in diameter; on this find the point where o eligbt diminution of pressure is indicated by the gauge. Just heyond this point insert aring of one inch orifice in the pipe, giving & ehoulder, all around, of *% inch, and the lost preeeure will be foundto have been restored. The reservoir has been virtually moved forward to this point. Repeating the operation at the same distance out from this point as from this to the reservoir produces the eame reeult, Each point or section of the pipe charges the succeeding with original force, and it would seem that there can he no limit to the principle. And now comes the Engineer and Mining Journal, and pricke the above-described bubble as followe: It is true that the pressure in the Spear pipe mnst he more unitorm than in other pipee. He obtains this advantage hy presenting not lees hut more friction to the advancingair. At given distancee he contrgcts his pipe so much, that to force a constant quantity of air through the narrow orifice, the pressure bas to increase until it equals that at the compreesor. This he puts down as a proof that he has eaved power? Had he put a cap on the end of his tube the result would have been the same, that ie the pressure would have been equal throughout the closed tube. Butin this case he would have economized no power, hecause the flow of the air would be entirely chut off. The difference between this case of a closed tube and that of 8, Spear tube, which is a partly closed one, is that in one case the power is entirely shut off, and in the other partially ao. In the one case the loss of power ie complete, in the other it depends upon the degree to which the power has been shut off. There is certainly nothing new in the fact that pressure can be maintained at a particular point hy partly closing up the tube. Other engineors than Mr. Goodwin have, however, been in the habit of coneidering that greater preeeure is obtained by sacrificing to a certain degrea the rapidity of flow, or increasing the motive power. The Engincer further refers Mr. Spear to an instance in which the old principle involved in tho contraction of pipee has been put in uee, and ingeniously so, in a new blowpipe reservoir deecribed in thet journal, in which the flow of air is diminished and the pressure increased, eo that a conatant blast is obtained, and eolely by the use of contracted orifices. A Three Cylinder Engine. A three eylinder engine is one of the noveltics recently desoribed in tho English mechani cal journal. In this engiue three oylinders are disposed round the crank shaft at an angle of one hundred and twenty degrees to each other, each cylinder being provided with a deep bunt light piston, from which a connecting rod is led to tho crank common to all. One of the connecting rods has a single eye at the erank end, whilo the two other rods are forked at that end, the fork of the one being wide enough to take hold of the pin outaide the other, so that the center lines of the rods are allon the same plane. The cylinders are all open at their inner ends, and when the engine is at work the steam from the hoiler has free acccss to the central space, so that it tends to forco the three pistons outward uniformly. The admission of the steam to, and its release from, the outer ends of these three cylinders is effected by a single revolving slide valve. This valve works against a face at one eide of the central chamber, being carried round with the crank shaft. As there is neceesarily eome throttling in the steam passages, particularly when the engine-is running fast, the pressure of tbe steam at the outer ends of the cylinders never equalathatin the central chamber,and hence the pistons are always forced outward. The etrain upon the connecting rode being always atensile one, but varying in amonnt according to whether the eteam is being admitted to or exhausted from the onter ends of the cylinders. Tae Inventor or THE CigcuLark Saw.—An exchange says: ‘'The inveution of the circular eaw is generally attrihuted to Captain Kendall, of Maine, who died a few weeks ago at the age of 89. This ien mistake. The circular saw wae invented by Joseph Mnrray of Mansfield, England, son of an old servant of the Byron family, whom Lord Byron, the peet, often speaks of in his letters ae ‘‘ Old Joe Murray.”’ The first saw of the kind ever made is etill shown by hie descendants.” AMERICAN vs, ENGLISH ENOINEERING.~-American iron hridgee are lighter than thoseef other nations, hnt their absolute strength ie as great, siuce the weight which is saved is all dead weight, and not necessary to the solidity of the etructure. The eame difference is displayed here that ie seenin our carriages with their slender wheels, as compared with the lumbering, heavy wagons of European construction. E : §cientiFic ‘Proaress. The Road to Scientifio Success. It is no longer possible to know everything. A universal scholar will be no longer geen among men. The range of human knowledge has increased so vastly, hes swept out and away so far and eo fast, that the brain, he ite quantity and quality what it may, cannot, in the years commonly given to man, even survey the field. A man, therefore, muet make up his mind, if he propose to learn anything, to be content with profouud ignorance of a great . many other things. It isa bitter thing, perhaps, butis the fact, that a man who would know anything in this century must purchaee hie knowledge with voluntary and chosen ignorance of 4 hundred other things. One must choose his epecialty, and devotion and diligence to the subject of his choice is the price he pays for success. It ie with doing it asitis with knowing. There is only a certain amount of work in either case. He can not do everything. Nevertheless, everything needs doing. All about him ie undone work clamoring for hauds. There are two courses before one. To undertake everything, to fret and grieve because one finds this and that undone, and to make apasmodic efforte to do it—thie is the way of failure. Resolutely to make up one’s mind to let, as far as he is concerned, the most should be undoue, stay undone still, to steel one’e heart against demands and necessities, to resist all inducements to put fortha single effort, to close one’s eyes to it all, and to etick heart, hand, life, and love to the thing a man undertakes and calls his own—thet is the way of euccese. Life is very short, and the eingls brain and hand, at best, very weak, and there are thousands of things to know and to do. One must choose, and be content with hie choice. And so it comes to pass that now at last the measure of a man’e learning will be the amount of his voluntary ignorance, the measure of his practical effectiveness the amount of what he is content to leave unattempted.—Golden Era. Screntiric Prenterrons.—A curious illustration of the power of scientific precision in the prediction of matters by no means dependent upon mathematical data, ie feund in a book on ‘The Coal Question’”’ in England, published more than eeven years ago, by Prof. Stanley Jevone, in which he predicted that the coal conaumption of England in 1871 would be 117,900,000 tons. In the volume of mineral etatistics of Great Britain for 1871, just published, the actual consumption is set down at 117,352,028 tone. Danwry axp Aoassiz.——Mr. Darwin attempts to prove from the variations of animals in domestication, corresponding variatione in a natural or wild state; and on these founds his theory of natural selectien. Prof. Agassiz attributed these variations in domestic animals to the intelligence of man, and holds that physical causes havo never been known to produce snch effects as the intelligent will of man is known to produce. However greatly the teachings of these savans may differ in their ultimate results, they both agree thet man does exert a very great influence on the animals which come under his immediate care; that animale in domestication do vary, and that man, taking advantage of these variations, does by systematic selection, aided by the great law of inheritauce, acoumulate in certain families or strains of domestio animals, such qualities of econemic valne as he may desire. These qualitieaor peenliar traits become, in the course of years, well established characteristics of the family or hreed, and are transmitted frem one generation to another with almost unerring certainty. In the language of the declaration ““ve hold these truths to be eelf-evident,’’ and while from them Mr. Darwin argues hie evolution theory, and Prof. Agassiz eulogizes the human intellect, we may confidently trust them as a safe basie from which to work. A Fuame Oroan.—At a meeting of a local ecientific body lately held at Ipswich, Exgland, an ingenious device was exhibited, which had been censtructed to give a practical exhibitien of the musical character of the aounds given out hy the burning of hydrogen gas in a tube. This fact wae made use of in the gae-flame organ exhibited, in which a seriee of jeta, nnmbering twenty, hurning in tubee of different leugths and propertionate sizes, were made tn produce a chromatic scale of notes. Enaoh tuhe was capped with a valve which was opened hy means of a connecting rod attached to a digitorium, and thue heautiful chords ceuld be struck, and simple meledies played at the will of the performer. Owing to the tubes being coustructed of glaes, the action of the flame could he seen. Mr, Goddard, the inventor and constructor of the instrument, played ‘Home, Sweet Home,’’ and other familiar airs, and hie audience were delighted with the enrrectness and melody of the musie. By meana of a long tube, the explosion of the gas buhblea which caused the mueical notes waa rendered visible, for, just as a lighted stick, if whirled round ata greater rate than the eighthof a second, cannot be follnwed by the eye in ite course, but appears as a ring of light, ao the rapidity with which the minute gaa exploesiona followed each other could not he perceived by ihe ear, the effect being that of centinuous notee, Buus Sey anp Warer.—Les Bfondes quotes from M. Collas the following remarkable views: He first refers to the blue color exhihited by the pure water of certain lakes, and aaya that it ie due to the therein diesnlved or very minutely divided gelatinoue ailica, quoting as instances the lake of Geneva, the ‘water of the d’Huie, and more particularly the water of a sourcenear to the Mont-Dore which water ‘seven bluish-colored when placed in a white glasa decanter. The blue color of the sky is referred by the author to the same causes, viz., ve finely divided gelatinoue silica (hydrated tien kept in suspension in the clouds on account of its great lightness, A correspondent in the Gas Light Journal thinks these hypothesiy have a plentiful lack of probalility. Still no more enrious chemical queetione exist that those connected with the dietribution of eilica in eoila, waters, etc. Asto silica in the air, except aa mere dust, that seems really beyond credibility. Taon in Savt Warer.—At a meeting of the Polytechnie Association of the American Institute, Mr. W. J. McAlpine said: “It is supposed that caet iron oxidizee rapidly in ealt water. I have eeen in Europe square piles that had been 47 years in salt water, with the weights marked on them, taken up and broken up, and no appreciable loss had taken place, Even the corners eeemed sharp and distinct. Here we see water pipes decomposed; and what ie the explanation? One kind of iron will decompose and another will not. Where the carhon and the metallic iron arein intimate chemicel combination, it will last 100 or 1,000 years, perhaps. The white or gray iron ie incorruptible, while the soft foundry iron decomposee readily. I have taken up water pipes that I myeelf laid 30 years ago, and fonnd them not corroded a particle. I have taken up others, which, as you took up a pipe, hroke to pieces.” Coat Om Fuet tn Rossta.—Successfn] experiments are aeid to have been recently made in Russia in the use of the products of coel oil for fuel for locomotives. The aame fuel has also been applied, with reported satisfactory resulta, * in the propulsion of eteamboats, ‘The engineers engaged in the experimenta report the accomplishment of more work with this fuel than ie obtained from the same value in ordinary {nels. 5 Scrence is etudied by the observation of facts, Bnt observation is not eaey. It requirea more memory and a further perepective than moat men possess. Experiment, too, is neceseary, which is a series of qnestione put to Nature, and no witness can he found more difficult to examine,

March 15, 1873.] MINING AND SCIENTIFIC PRESS. 163 I ECHANICAL sP RoaRESS The Band Saw and Ban Sawing. (Continued.] In continuing our extract from the very interesting article on ‘‘ Band Saws’’ from Riehards’ treatise on Wood-Working, which we noticed last week, we now come to the subject. Band Saw Blades. ‘Tho bladea for hand sawsshnuld have what is technically known as ain 4 temper, or if different, a shade above in hardness. If much harder, they are liahle to fracture from irregular tension, or concussion of any kind, expensive to aharpen, and difficult to set without breaking the tceth. Rendered sefter than this, thoy are simply worthless, and should have no market value. Theamonnt or degree of teinper in a saw blade is quite an ohscure matter, one that eannot be determine 1 to any certainty by observation, and hardly hy experimont, fer although a blado ie properly tempered throughout nine-tenths of ita length, anal certain spota are drawn, agis often thecase in grinding, or glazing, the hlade is more worthless than if eoft throughout. The purchasers of sawa are, therefore, incapable of testing the quality of the eawe, and the time of buying muet depend upon the geod faith of the manufacturers, who usually, and very properly too, are understood as guaranteeing the saw tn be of even and good temper, and of fine ateel. Tho working quality, and indeed the whole value of the caw, isin great measure dependent upon tne eare and skill of the saw maker, of which there exist no evidence, or at leaet un ise facie evidence in the appearance of the blades when finiched. In celecting hand-saw blades a goed plan ie to roll the ends closely, and ace if tbey will epring back te their first pesition. The texture of the eteel can be examined by breaking ashort piece from the end, the differance hetween coarse granular fracture, and fine lvely-looking steel heing familiar matter to most mechanics. To determine the etraightness of the blade if not joined, unroll it on the floor, and by ‘‘sighting it,”’ irregularities are eacily detected. Another mnst important matter ie an exact parallel as to width; the slightest variation in this regard becomes a aerioua objection to “the operation of 2 saw, preducing ecratches on the work, irregular action of the teeth, and consequent irregular tension of the blade through its cutting at intervale ouly. Any variation of width between the two ende of a blade can be easily detected by lapping them, and miecing tha points of the teeth ona plane anrface, which will ahow on the backe any differance of width, however little it may 0. The pitch, depth, and form of teeth for band sawa, is a matter abont which there is snch a diversity of npinion, that the only safe inference ie, that it is either a matter of no great importance, or else not understood. Wealludeof course to eaws for epecial purposea; for varioue modificatione of the teeth are needed in different cases, and unfortunately the condition that has most to do with the change is continually varying, that is, the depth of the lumber. In considering caw teeth, we have fira', pitch (distance hetween teeth); the inclination on front aud back of the tooth (cutting angle); the form of the gullet, as it is termed, for holding the dust; the width of the haae of the tooth, eo as to give eufficient stiffness to retain the “set”; and the kind of set given to the teeth. It would be supposed that the experience of operating other saws would furnish all that could be learned of baud saws, hut thie doee not seem by any means to be the case. The thinneee of the hlades calls for every minute condition that will tend to keen them true, and toruninline. With a thick circular, or reciprocating aaw, the caeeis different; it can he forced to its work, and made to operate without that nice regard to the condition and form of the teeth that must he ohserved in band eawing. For aoft wood, a pitch equal to one-half, and a depth equal to one-fifth of the width of the blade, ie as near a general rule as can at this time be euggested. For hard wood a closer pitch of one-third the width is. better. The gullet or throat under the tooth should in all caaes be circular; not only to guard against breaking or checking in the cornere, but to revent the dust from lodging; ae with an acute angle it can be carried in quantities on to the wheels, For the front inclination of the teeth, it ehould be eufficient, eo that when. the sawia aharp there will be no back thrust on bladea; a thing that must in each case be determined by the observation of the operator, and the character of the timber to be ont. . In the matter of setting, it must be determined by the thicknese of the blade and character of the wood. In sawing pine, or other soft woods, the teeth can be bent from the base, and will retain their set; but in hard wood or knote this kind of setting does not last long, but eoon “‘ cumee ont,’’ to uee a lumberman’s expression. Upsetting the teeth ie impracticable with thin eaws, or at least ie very difficult, unieaa the plates are No. 14 or thicker. The temper besides is, or ought to be, too high in band sawe for upsetting. The best plan of seting developed in the writer’s experience, in band eawing, is a 5 acy abrupt bend on the bottom of the tooth by ‘‘sharp hlows’’ from a light hammer—setting the steel, n3 it were, off to one side and raising a kink of scraping edge on the entting side of the tooth. It is easy to get a regular or smeoth set in this manner, and it requirs no special skill to perform it; it is besides sooner done, no gauge heing required. Thosaw is passed over an anvil, with is top bevelled to a proper angle, tho hotton: cdge of the toeth projecting over tho bevel, from the sixtcenth to one-eight of an inch, according to the amount of set required. ; These remarks upon toeth relato to saws intended for power or positive speed. For screll sawing or plain had slitting it is presumed that no information of any interest could he given, and that none is needed. {To be Continued.] Conveying Air Through Pipes. A Supposed Valuable Invenlicn Explained Away. We sometime since gave a description of a new device for conveying compressed air through pipes for motive pnwer, wherehy it was suppesed the friction of the air upon the walls of the tubs was done away with. The invention may be auhstantially described ns followe :— Jf, ina pipe nf twelve inches diameter we make at intervals necks of ten inches in diameter, we have an annular space one inch deep around the inner circumference of the pipe. The theery is that the air contaiued in this epace does not meve, but remains at rest, and thue presents an air eurface te the meving mase of air ten inehes in diameter which flows threugh the necke. As the friction ofair on air is leos than that ef air on iron, he expects to convey power in the ehape of compressed air with almost no loss frem friction. The invention is claimed by a Mr. Spear, of Bostou, and the marvel wasendorsed hy Willium A. Goodwin, ‘‘city engineer of Portland, and for aome years gevernment lighthouse engineer,’’ who had given the invention a practical trial, and, as he supposed a thorough teet as follows: He set a pressure gauge on a reservoir which received cempressed eir, and when a pressure of 40 lbs. was indicated, opened an orifice in the reservoir so large ae to exhaust the effect of the compressor as faet as delivered. The compreesor is now working into the reservoir, the orifice blowing off and the gauge stands at 40. Suppose the orifice to be one inoh in diameter. Now attach to the same a pipe of one inch in calihre, eay 100 feet long. Ata point near the onter end of this pipe seta pressure gauge, and the preesure with the pipe wide open, will he found to be something less than 40 Ibs. The element of friction has been developed in the pipe. Now take an additional pipe 124 inches in diameter; on this find the point where o eligbt diminution of pressure is indicated by the gauge. Just heyond this point insert aring of one inch orifice in the pipe, giving & ehoulder, all around, of *% inch, and the lost preeeure will be foundto have been restored. The reservoir has been virtually moved forward to this point. Repeating the operation at the same distance out from this point as from this to the reservoir produces the eame reeult, Each point or section of the pipe charges the succeeding with original force, and it would seem that there can he no limit to the principle. And now comes the Engineer and Mining Journal, and pricke the above-described bubble as followe: It is true that the pressure in the Spear pipe mnst he more unitorm than in other pipee. He obtains this advantage hy presenting not lees hut more friction to the advancingair. At given distancee he contrgcts his pipe so much, that to force a constant quantity of air through the narrow orifice, the pressure bas to increase until it equals that at the compreesor. This he puts down as a proof that he has eaved power? Had he put a cap on the end of his tube the result would have been the same, that ie the pressure would have been equal throughout the closed tube. Butin this case he would have economized no power, hecause the flow of the air would be entirely chut off. The difference between this case of a closed tube and that of 8, Spear tube, which is a partly closed one, is that in one case the power is entirely shut off, and in the other partially ao. In the one case the loss of power ie complete, in the other it depends upon the degree to which the power has been shut off. There is certainly nothing new in the fact that pressure can be maintained at a particular point hy partly closing up the tube. Other engineors than Mr. Goodwin have, however, been in the habit of coneidering that greater preeeure is obtained by sacrificing to a certain degrea the rapidity of flow, or increasing the motive power. The Engincer further refers Mr. Spear to an instance in which the old principle involved in tho contraction of pipee has been put in uee, and ingeniously so, in a new blowpipe reservoir deecribed in thet journal, in which the flow of air is diminished and the pressure increased, eo that a conatant blast is obtained, and eolely

by the use of contracted orifices. A Three Cylinder Engine. A three eylinder engine is one of the noveltics recently desoribed in tho English mechani cal journal. In this engiue three oylinders are disposed round the crank shaft at an angle of one hundred and twenty degrees to each other, each cylinder being provided with a deep bunt light piston, from which a connecting rod is led to tho crank common to all. One of the connecting rods has a single eye at the erank end, whilo the two other rods are forked at that end, the fork of the one being wide enough to take hold of the pin outaide the other, so that the center lines of the rods are allon the same plane. The cylinders are all open at their inner ends, and when the engine is at work the steam from the hoiler has free acccss to the central space, so that it tends to forco the three pistons outward uniformly. The admission of the steam to, and its release from, the outer ends of these three cylinders is effected by a single revolving slide valve. This valve works against a face at one eide of the central chamber, being carried round with the crank shaft. As there is neceesarily eome throttling in the steam passages, particularly when the engine-is running fast, the pressure of tbe steam at the outer ends of the cylinders never equalathatin the central chamber,and hence the pistons are always forced outward. The etrain upon the connecting rode being always atensile one, but varying in amonnt according to whether the eteam is being admitted to or exhausted from the onter ends of the cylinders. Tae Inventor or THE CigcuLark Saw.—An exchange says: ‘'The inveution of the circular eaw is generally attrihuted to Captain Kendall, of Maine, who died a few weeks ago at the age of 89. This ien mistake. The circular saw wae invented by Joseph Mnrray of Mansfield, England, son of an old servant of the Byron family, whom Lord Byron, the peet, often speaks of in his letters ae ‘‘ Old Joe Murray.”’ The first saw of the kind ever made is etill shown by hie descendants.” AMERICAN vs, ENGLISH ENOINEERING.~-American iron hridgee are lighter than thoseef other nations, hnt their absolute strength ie as great, siuce the weight which is saved is all dead weight, and not necessary to the solidity of the etructure. The eame difference is displayed here that ie seenin our carriages with their slender wheels, as compared with the lumbering, heavy wagons of European construction. E : §cientiFic ‘Proaress. The Road to Scientifio Success. It is no longer possible to know everything. A universal scholar will be no longer geen among men. The range of human knowledge has increased so vastly, hes swept out and away so far and eo fast, that the brain, he ite quantity and quality what it may, cannot, in the years commonly given to man, even survey the field. A man, therefore, muet make up his mind, if he propose to learn anything, to be content with profouud ignorance of a great . many other things. It isa bitter thing, perhaps, butis the fact, that a man who would know anything in this century must purchaee hie knowledge with voluntary and chosen ignorance of 4 hundred other things. One must choose his epecialty, and devotion and diligence to the subject of his choice is the price he pays for success. It ie with doing it asitis with knowing. There is only a certain amount of work in either case. He can not do everything. Nevertheless, everything needs doing. All about him ie undone work clamoring for hauds. There are two courses before one. To undertake everything, to fret and grieve because one finds this and that undone, and to make apasmodic efforte to do it—thie is the way of failure. Resolutely to make up one’s mind to let, as far as he is concerned, the most should be undoue, stay undone still, to steel one’e heart against demands and necessities, to resist all inducements to put fortha single effort, to close one’s eyes to it all, and to etick heart, hand, life, and love to the thing a man undertakes and calls his own—thet is the way of euccese. Life is very short, and the eingls brain and hand, at best, very weak, and there are thousands of things to know and to do. One must choose, and be content with hie choice. And so it comes to pass that now at last the measure of a man’e learning will be the amount of his voluntary ignorance, the measure of his practical effectiveness the amount of what he is content to leave unattempted.—Golden Era. Screntiric Prenterrons.—A curious illustration of the power of scientific precision in the prediction of matters by no means dependent upon mathematical data, ie feund in a book on ‘The Coal Question’”’ in England, published more than eeven years ago, by Prof. Stanley Jevone, in which he predicted that the coal conaumption of England in 1871 would be 117,900,000 tons. In the volume of mineral etatistics of Great Britain for 1871, just published, the actual consumption is set down at 117,352,028 tone. Danwry axp Aoassiz.——Mr. Darwin attempts to prove from the variations of animals in domestication, corresponding variatione in a natural or wild state; and on these founds his theory of natural selectien. Prof. Agassiz attributed these variations in domestic animals to the intelligence of man, and holds that physical causes havo never been known to produce snch effects as the intelligent will of man is known to produce. However greatly the teachings of these savans may differ in their ultimate results, they both agree thet man does exert a very great influence on the animals which come under his immediate care; that animale in domestication do vary, and that man, taking advantage of these variations, does by systematic selection, aided by the great law of inheritauce, acoumulate in certain families or strains of domestio animals, such qualities of econemic valne as he may desire. These qualitieaor peenliar traits become, in the course of years, well established characteristics of the family or hreed, and are transmitted frem one generation to another with almost unerring certainty. In the language of the declaration ““ve hold these truths to be eelf-evident,’’ and while from them Mr. Darwin argues hie evolution theory, and Prof. Agassiz eulogizes the human intellect, we may confidently trust them as a safe basie from which to work. A Fuame Oroan.—At a meeting of a local ecientific body lately held at Ipswich, Exgland, an ingenious device was exhibited, which had been censtructed to give a practical exhibitien of the musical character of the aounds given out hy the burning of hydrogen gas in a tube. This fact wae made use of in the gae-flame organ exhibited, in which a seriee of jeta, nnmbering twenty, hurning in tubee of different leugths and propertionate sizes, were made tn produce a chromatic scale of notes. Enaoh tuhe was capped with a valve which was opened hy means of a connecting rod attached to a digitorium, and thue heautiful chords ceuld be struck, and simple meledies played at the will of the performer. Owing to the tubes being coustructed of glaes, the action of the flame could he seen. Mr, Goddard, the inventor and constructor of the instrument, played ‘Home, Sweet Home,’’ and other familiar airs, and hie audience were delighted with the enrrectness and melody of the musie. By meana of a long tube, the explosion of the gas buhblea which caused the mueical notes waa rendered visible, for, just as a lighted stick, if whirled round ata greater rate than the eighthof a second, cannot be follnwed by the eye in ite course, but appears as a ring of light, ao the rapidity with which the minute gaa exploesiona followed each other could not he perceived by ihe ear, the effect being that of centinuous notee, Buus Sey anp Warer.—Les Bfondes quotes from M. Collas the following remarkable views: He first refers to the blue color exhihited by the pure water of certain lakes, and aaya that it ie due to the therein diesnlved or very minutely divided gelatinoue ailica, quoting as instances the lake of Geneva, the ‘water of the d’Huie, and more particularly the water of a sourcenear to the Mont-Dore which water ‘seven bluish-colored when placed in a white glasa decanter. The blue color of the sky is referred by the author to the same causes, viz., ve finely divided gelatinoue silica (hydrated tien kept in suspension in the clouds on account of its great lightness, A correspondent in the Gas Light Journal thinks these hypothesiy have a plentiful lack of probalility. Still no more enrious chemical queetione exist that those connected with the dietribution of eilica in eoila, waters, etc. Asto silica in the air, except aa mere dust, that seems really beyond credibility. Taon in Savt Warer.—At a meeting of the Polytechnie Association of the American Institute, Mr. W. J. McAlpine said: “It is supposed that caet iron oxidizee rapidly in ealt water. I have eeen in Europe square piles that had been 47 years in salt water, with the weights marked on them, taken up and broken up, and no appreciable loss had taken place, Even the corners eeemed sharp and distinct. Here we see water pipes decomposed; and what ie the explanation? One kind of iron will decompose and another will not. Where the carhon and the metallic iron arein intimate chemicel combination, it will last 100 or 1,000 years, perhaps. The white or gray iron ie incorruptible, while the soft foundry iron decomposee readily. I have taken up water pipes that I myeelf laid 30 years ago, and fonnd them not corroded a particle. I have taken up others, which, as you took up a pipe, hroke to pieces.” Coat Om Fuet tn Rossta.—Successfn] experiments are aeid to have been recently made in Russia in the use of the products of coel oil for fuel for locomotives. The aame fuel has also been applied, with reported satisfactory resulta, * in the propulsion of eteamboats, ‘The engineers engaged in the experimenta report the accomplishment of more work with this fuel than ie obtained from the same value in ordinary {nels. 5 Scrence is etudied by the observation of facts, Bnt observation is not eaey. It requirea more memory and a further perepective than moat men possess. Experiment, too, is neceseary, which is a series of qnestione put to Nature, and no witness can he found more difficult to examine,