MECHANICAL IMPROVEMENTS AND INVENTIONS. 



517 





reotlon of the periphery, instead of radially or 

 tangentially. 



A i ink of artificial ice for summer skating 

 has been provided by a Mr. Gamgee, in Eng- 

 land, and has found much favor. The glacia- 

 ri'tii,. as it is called, differs from the other con- 

 trivances of its kind principally in the use of 

 glycerine and water as a refrigerating medium 

 iii-tcu<l of brine, which is destructive to metal- 

 lic surfaces. Iron pipes of rectangular section 

 are imbedded in a concrete bottom, with their 

 upper surface only exposed. The water to be 

 congealed is contained in this concrete trough, 

 and is about two inches deep. The glycerine 

 and water, which remains fluid at a tempera- 

 ture below zero, after passing through the re- 

 frigerator is pumped up into a tank from which 

 it flows steadily through the iron pipes and 

 into the refrigerator again. But, before enter- 

 ing the main refrigerator, its temperature is 

 reduced by letting it flow through a worm sur- 

 rounded by the powdered ice swept from the 

 rink mixed with salt. The refrigerator is an 

 ether-machine, in which a steam-power air- 

 pump exhausts the ether from the refrigerat- 

 ing chamber and forces it into a condenser. 

 The ether is brought into proximity with the 

 glycerine mixture in a copper box with round 

 holes passing through it ; the box is sur- 

 rounded by a wooden tank through which 

 the glycerine mixture is constantly flowing. 

 The ether, as well as the congealing mixture, 

 is in constant motion, passing from the refrig- 

 erator into the condenser and back again in a 

 steady flow. 



The Lowe water-gas process, in which the 

 difficulties that attended former efforts to ob- 

 tain illuminating gas by the decomposition of 

 water were sufficiently overcome to give prac- 

 tical value to this method, was first put into 

 successful operation at Phoenixville, Pa., about 

 three years since. Works were built at Utica 

 in 1874, which were afterward destroyed by fire. 

 This year a still larger establishment has gone 

 into operation at Manayunk, near Philadelphia, 

 and others are opening in several large towns 

 of the Northern States and Canada. The Mana- 

 yunk works produce about 150,000 feet of 

 twenty-candle gas daily, though their capacity 

 is more than double that quantity. The works 

 occupy only a tenth of the space that is re- 

 quired in coal-gas manufacture. The plant 

 consists of three generators ten feet six inches 

 in height, with an internal diameter of forty 

 inches ; six superheaters, three to superheat the 

 steam and three to fix the gas, each fifteen feet 

 high with thirty-four inches internal diame- 

 ter, and condensers, purifiers, etc. The labor of 

 seven men only is employed for the present 

 production, three in the night and four by day. 

 The cost of the gas is, considering its superior 

 quality, something like one-half that of the gas 

 manufactured by the old process. About three 

 gallons of petroleum are consumed in the pro- 

 duction of 1,000 cubic feet. The process is very 

 much quicker than the old one. This method 



of acquiring a combustible gas, by the action 

 of burning carbon upon superheated Bteam, 

 easily and cheaply, now sufficiently tested, 

 opens up great possibilities of economical heat 

 as well as light in the future. The problem of 

 the saving of the 80 or 85 per cent, of heat- 

 effect, now wasted in the combustion of fuel 

 in the most perfect heat-generators, seems ap- 

 proaching its solution. 



The process of toughening glass consists in 

 cooling it rapidly by plunging it in a bath of 

 grease, after it has been shaped, annealed, and 

 reheated to redness. The effect is to cause 

 a different primary arrangement of the mo- 

 lecular particles ; toughened glass is less dense 

 than ordinary glass, and when broken does not 

 present sharp edges. To be successfully tough- 

 ened it must be reduced to a malleable and pasty 

 consistency, but will lose its shape if too soft. 

 The more rapidly the cooling takes place, the 

 more perfectly the glass is toughened : but to 

 low a temperature will cause the glass to break. 

 The temperature at which the toughening can 

 take place vares according to the composition 

 of the material, and the size and thickness of 

 the article. Crystal made of six parts of sand 

 to two of potash and soda and one of red lead 

 succeeds the best. The temperature of the 

 bath for crystal, in which pure grease is used, 

 may be from 60 to 120 centigrade. For 

 glass grease mixed with oil is used, and the 

 hardening is produced at a temperature of 150 

 to 300 C. The process described is the one 

 of M. de la Bastie. The other process resem- 

 bles it in all important particulars. Many im- 

 provements have been introduced lately. 



Julius Bluethner, of Leipsic, whose piano- 

 forte factory is one of the largest and com- 

 pletest in Europe, has made a study of the tech- 

 nical application of the important principles 

 of acoustics recently discovered, preeminently 

 through the investigations of Helmholtz. He 

 has succeeded in making these scientific dis- 

 coveries practically available in an instrument 

 which he manufactures under the name of the 

 aliquot piano. Among all the important im- 

 provements introduced within the last twelve 

 years in the manufacture of this most valuable 

 musical instrument, this of Herr Bluethner will, 

 beyond dispute, take the foremost rank. As 

 the name implies, the aliquot piano renders 

 the quality called timbre in tone, whose nature 

 has been explained by Helmholtz's analysis of 

 physical sounds. The harmonious upper notes 

 detected by Helmholtz, and the so-called com- 

 bination-tones, into which the lower octave 

 enters, are emphasized in this instrument by 

 the simultaneous vibration, by a mechanical 

 attachment, of their appropriate strings. To 

 successfully accomplish this object, it was ne- 

 cessary to entirely change the construction of 

 the instrument, to change the pedal-arrange- 

 ment, and to employ seventy-two more strings 

 for pianos of the ordinary size. The difficulties 

 have been so successfully overcome that the 

 new instrument is as easy to tune as the others, 



