TRANSACTIONS OF THE SECTIONS. 35 



Account of Experiments on Heating hy Steam, By W. West. 



These experiments were instituted for the purpose of ascertaining if water heated 

 by steam readied the true boihng temperature. In several experiments it was found 

 that although the water was violently agitated, and steam escaped in abundance, that 

 the thermometer indicated 190°, 205°, and 207°, and could not be raised to the true 

 boiling-point. A false bottom being added to the receiving vessel pierced with nu- 

 merous small holes, it was found easy, with even a smaller quantity of steam, to main- 

 tain the temperature at 212°. 



On a i^eculiar Condition of Zinc, produced hy a long-continued High 

 Temperature. By Thomas Tilley, Ph.D. 



Dr. Tilley presented a specimen of zinc, which had undergone a remarkable change 

 in its arrangement, from being kept at a heat above that of fusion for a considerable 

 time. This cliange was thought to bear some analogy to the alterations which sulphur 

 and some other bodies are known to undergo at different temperatures. The condi- 

 tion of the zinc was singularly crystalline. The zinc in this state was found to have tlie 

 same chemical condition as the ordinary zinc of commerce, and, although its oxides 

 and salts have not been examined, it was found that, when distilled, the zinc was re- 

 stored to its original texture. It was suggested, that many interesting examples of 

 similar molecular changes in other metals might be detected by subjecting them to 

 similar conditions to those in which this sample of zinc was placed. 



Description of an Air-Duct to be used in Glass Furnaces for the Prevention of 

 Smoke, with Models. By T. M. Greenhow. 



The nuisance of smoke it is assumed must be prevented by the supply, under proper 

 conditions, of additional quantities of oxygen gas to the burning matter, so as to ren- 

 der its combustion complete. Though this intention has been successfully carried 

 out in steam-engine and other furnaces, no attempt has been successful to prevent tlie 

 annoyance occasioned by glass furnaces. One of Mr. Greenhow's models represented 

 the reverberatory furnace used in the manufacture of crown glass. In this kind of fur- 

 nace the smoke and products of combustion escape through the openings in the sides 

 wliich give the workmen access to the pots of glass, and are unprovided with flues. To 

 provide the necessary .supply of fresh air, Mr. Greenhow proposes a perpendicular air- 

 duct (made of the same refractory clay of which the glass pots are constructed) rising 

 through the middle of the fire, and suppoi-ted by the stone arch on which the bars rest. 

 This air-duct rises to the height of five feet within the furnace, is one foot in diameter, 

 and distributes, through numerous apertures, any quantity of air that may be required 

 for the completion of the combustion of the fuel ; and from its situation in the centre 

 of the furnace it must soon acquire and communicate a high degree of temperature to 

 the air it transmits. Mr. Greenhow showed a second model of a steam-engine fur- 

 nace with a horizontal air-duct placed anterior to the bridge, which it crowns and 

 overlaps. A t this situation heated air is distributed through small apertures, so as to 

 mingle with the burning gases and ensure their more complete combustion. 



On the Influence of Light on Chemical Compounds, and Electro-Chemical 

 Action. By Robert Hunt. 



After alluding to Sir John Herschel's experiments on the chloride of platinum, neu- 

 tralized by lime water, from which a platinate of lime was precipitated by the influence 

 of the solar rays, and to Dr. Draper's observations on the power which the solar beams 

 had of imparting a property to chlorine of uniting with hydrogen under circumstances 

 in which the same elements kept in the dark would not unite, Mr. Hunt called atten- 

 tion to some experiments in which still more remarkable results had been obtained. If 

 a solution of mineral chameleon be made in the dark it does not undergo any change 

 for many hours, whilst a similar solution will, if exposed to sunshine, precipitate 

 heavily almost immediately. Sulphate of iron dissolved in com.mon water, will, even 

 in the dark, after some hours, give a precipitate of carbonate of iron ; but if exposed 



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