Chcimstry and Mineralogy. 397 



statement gave rise to observations on the part of several gen- 

 tlemen who differed from Mr Hartop, as the reduction in the 

 price of iron from hot air had not occurred in other parts of 

 the country, and that, as prepared in Glasgow, and many other 

 places, it had not been so deteriorated. It has, in consequence, 

 been adopted in every smelting-house in Scotland, and the an- 

 nual produce of the works in that country during the last ten 

 years has been nearly doubled. Reference was also made to 

 processes adopted in the Russian smelting-works, which shewed 

 that, by a judicious adjustment of the quantity of cold air intro- 

 duced by the blast, a saving could be effected approaching even 

 to that obtained by the use of hot air. 



17. A letter was then read from Colonel Colby, accompanied by 

 a copy of the ordnance survey of the county of Londonderry, 

 in the hope that the Section might suggest some improvements, 

 or additional topics of consideration to be introduced into the 

 survey. 



18. A paper was then read by Dr Apjohn on a new method of 

 determining the specific heats of the gases. Having arrived at 

 an accurate formula representing the relation between the tem- 

 perature of the wet-bulb thermometer and dew-point, including 

 the specific heat of air as a coefficient, he was enabled, by obser- 

 vations of the depression in perfectly dry air, and the application 

 of the formula in question, to determine the specific heat, not 

 only of air, but of a variety of other elastic fluids. His results 

 are, that all gases but hydrogen have, under equal volumes, 

 specific heats proportional to their specific gravities; so that, 

 with the exception just mentioned, all have, under equal weights, 

 the same capacity for caloric. 



19. Dr Dalton introduced the subject of a system of chemical 

 symbols, by explaining his ideas respecting the composition of 

 the simple compounds, and exhibited the expressions which he 

 proposed many years ago, to give a pictorial view of the mode 

 in which the atoms are collocated. He considers the composi- 

 tion of nitrous oxide to be two atoms azote, adopted by Berze- 

 lius, who has not stated from whom he obtained it. Olefiant 

 gas, he considers, is composed of single atoms of carbon and hy- 

 drogen, while the gas which exists in coal, though commonly 

 termed olefiant gas, is, in reality, double olefiant gas, and is 



VOL. XIX. NO. XXXVIII.— OCTOBER 1835. D d 



