REPORT— 1839. 171 



On the action of Air and Water upon Iron, 8fc. 



Mr. Mallett reported the progress of the investigation on 

 his subject, which was entrusted to Professor E. Davy and 

 himself, and stated his expectation, that a full Report of the 

 Results of the experiments would be presented to the next 

 Meeting of the Association. (See Report for 1838.) 



Report on a Machine for the detection and measurement of 

 Gases present in small quantities in Atmospheric Air, Coal- 

 Gas, Sfc, By William West. 



This instrument consists of a gasmeter turned slowly round by 

 clockwork, so as to draw the air, or other mixture of gases 

 under examination, through liquids proper to combine with and 

 detain the gases sought, as solution of lime or barytes for car- 

 bonic acid, a dilute acid for ammonia, a salt of lead for hydro- 

 sulphuric acid, &c. The hands on the clock-face denote the 

 volume of air thus submitted to partial analysis, and from the 

 weight of the new compound formed in the liquids the propor- 

 tion of foreign gases separated may be obtained by calculation. 



The advantage of this apparatus over the former modes of 

 attempting the same object, consists in the large quantity which 

 can thus be examined, several hundred cubic feet for instance, 

 instead of a few inches. It is intended to apply the apparatus 

 to the examination of the air of towns, by simultaneous experi- 

 ments with machines in the town and the adjacent country, 

 some of these to be at different distances and variously placed 

 as to the direction of the wind. These experiments will require 

 longer time and additional apparatus. The principle has been 

 successfully applied to measure the proportions of sulphuretted 

 hydrogen, and of ammonia in coal-gas. 



On the subject of a resolution adopted by the Meeting of the 

 British Association held at Newcastle, in August 1838, to the 

 following effect : — 



"Resolved, — ^That it is desirable that the whole of the stars 

 observed by Lacaille at the Cape of Good Hope, the observa- 

 tions of which are recorded in his Ccelum Australe Stelliferum, 

 should be reduced. 



" That Sir J. Herschel, Mr. Airy, and Mr. Henderson, be a 

 Committee for carrying the same into effect, and that 200/. be 

 appropriated for the purpose." 



