148 Institution of Civil Engineers. 



the author has established the fact, that reproduction of lost parts 

 takes place in metabolic as well as in the ametabolic articulata. 



The paper is accompanied with drawings of reproduced parts. 



5. " On the Changes of Temperature produced by the Rarefaction 

 and Condensation of Air." By James Prescott Joule, Esq. Com- 

 municated by P. M. Roget, M.D., Sec. R.S. 



In order to estimate with greater accuracy than has hitherto been 

 done the quantities of heat evolved or absorbed during the conden- 

 sation or rarefaction of atmospheric air, the author contrived an 

 apparatus where both the condensing pump and the receiver were 

 immersed in a large quantity of water, the changes in the tempe- 

 rature of which were ascertained by a thermometer of extreme sen- 

 sibility. By comparing the amount of force expended in condensing 

 air in the receiver with the quantity of heat evolved, after deducting 

 that which was the effect of friction, it was found that a mechanical 

 force, capable of raising 823 pounds to the height of one foot, must 

 be applied in the condensation of air, in order to raise the tempe- 

 rature of one pound of water one degree of Fahrenheit's scale. In 

 another experiment, when air condensed in one vessel was allowed 

 to pass into another vessel from which the air had been exhausted, 

 both vessels being immersed in a large receiver full of water, no 

 change of temperature took place, no mechanical power having been 

 developed. The author considers these results as strongly corro- 

 borating the dynamical theory of the nature of heat, in opposition 

 to that which ascribes to it materiality ; but he reserves the further 

 discussion of this question to a future communication, which he 

 hopes soon to present to the Royal Society. 



INSTITUTION OF CIVIL ENGINEERS. 



Junel 1,1844. — A paper on the purifying of coal gas, and the ap- 

 plication of the products thereby obtained to agricultural and other 

 purposes, by Mr. Angus CroU, was read. The process consists in 

 passing the gas through a solution of sulphuric acid, of the 

 strength of two and a half pounds of oil of vitriol to 100 gallons 

 of water, and by a continuous supply of acid, so that the proper 

 amount of free acid might be always kept in the vessel : the whole 

 of the ammonia in the gas was abstracted, preventing the cor- 

 rosive effect of this impurity of the fittings and meters through 

 which it was transmitted, and rendering the gas capable of being 

 used in dwelling-houses, and also enabling the gas companies to use 

 dry lime, instead of wet lime purifiers without producing any nuisance 

 on the opening of the vessels, by which a considerable saving was 

 effected, while at the same time sulphate of ammonia of great purity 

 ■was obtained, and of such a strength, that the evaporation of one gal- 

 lon produced eighty ounces of this valuable salt, instead of fourteen 

 ounces, which was the quantity rendered under the former process. 

 The author concluded by showing the advantage to agriculture by 

 the application of this produce ; he stated that various experiments 

 upon an extensive scale had been tried with this manure with great 

 success : one example will suffice for giving an idea of its powers. 



