202 Proceedings of the British Association for [Sept. 



14. Mr. Snow Harris exhibited an apparatus or modified 

 electrometer, for performing the experiments of Pouillet, 

 by which the insulation of the gold leaves is rendered in- 

 dependent of the glass, by means of two rods, terminating 

 in gilded balls. To determine whether electricity is deve- 

 loped during the evaporation of water or any liquid, a 

 platinum crucible containing the substance to be examined, 

 is placed upon the cap of the electrometer, having one of 

 Deluc's small piles communicating with the rods. His re- 

 sults were contrary to those of Pouillet. 



15. Dr. Newbigging made some observations upon an 

 experiment which he had made with regard to the colour 

 of arterial blood. He placed some blood in a cup containing 

 green spots on its surface. The portions opposite to these 

 spots assumed a vermilion colour, but in no other part was 

 this change visible. 



Thursday, \3th August. — 16. Mr. Hartop made some ob- 

 servations on the effect of the hot air blast, when applied to 

 the manufacture of iron. He opposed some of the state- 

 ments made by Dr. Clark at the last meeting of the Associa- 

 tion, relative to the increase in the product and the quality 

 of the iron ; the former having been overrated, and the latter 

 being decidedly inferior, as far as Yorkshire was concerned. 



17. Dr. Apjohn explained a formula for ascertaining the 

 specific heat of gases ; the expression being 

 /.//_ /./ ^ Sad p 

 ^ "J T~ "" 30 

 He has found it to correspond almost exactly with experi- 

 ment. He modifies it to 



. (f'-f")e 30 

 48 (i p 



If the air be quite dry, the/" (which expresses the elastic 

 force of vapour at the dew point) will be unnecessary, and 

 the formula becomes 



48rf ;? 

 The experiments were made by means of a syphon with 

 short horizontal arms. Sulphuric acid was introduced into 

 the legs. Two bladders, the one filled with common air, 



* These formulae are elucidated in a paper in the last Volume of the Trans, of 

 Che Irish Academy. 



