57 



Ordinary Meeting, February 18th, 1873. 

 E. W. BiNNEY, F.RS., F.G.S, Vice-President, in the Chair. 



I 



Scal& 



12, 



Dr. Joule, F.R.S., gave some 

 further account of the improve- 

 ments he had made in his air 

 exhausting apparatus. As 

 stated in the last Proceedings, 

 he had substituted a caout- 

 chouc tube attached to the 

 neck of a glass vessel, for the 

 original perpendicular pipe 

 with its stop-cock. This is 

 seen in the adjoining sketch c 

 and c?. The two positions, viz. 

 when h is being filled, and 

 when it is being emptied, are 

 shown by tlie full and the dot- 

 ted drawing. It is convenient 

 to introduce no air into d ex- 

 cept that required to act as a . 

 cushion to avoid a shock when 

 filled in the lower position. 

 Sulphuric acid may be intro- 

 duced into the receiver to be 

 exhausted, but it is perhaps 

 more convenient to place it 

 over the mercury in a, whence 

 it may occasionally be drawn 

 into h, to eff'ect the drying of 

 the internal parts of the appa- 

 ratus. Dr. Joule has met with 

 some difficulty in using mer- 

 cury gauges to ascertain the '\\ /''' 

 residual pressure, inasmuch as ''->.-,-.-_-;::-'-'' 

 Peoceedixgs— Lit. & Phil. Society.— Vol. XII.— Xo. 7.— Session 1872-3. 





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