ON THE EXPANSION OP ELASTIC FLUIDS. \$\ 



part of the fcale. Thefe conclufions were fo extremely dif- 

 cordant with and even contradictory to thofe of others, that I 

 could not but fufpecl fome great fallacy in them, and found it 

 in reality to be the fact : I have no doubt it arofe from the 

 want of due care to keep the apparatus and materials free 

 from moifture. 



My method of experimenting on this fubject is (imple, and The author's 

 therefore lefs liable to error. A ftraight manometer tube, jgjjjj* ^^, 

 fuch as has been mentioned, is duly divided into equal por-ter tube, 

 tions of capacity ; it is then dried by a wire and thread, and 

 the open end inferted through a cork into a phial containing 

 iulphuric acid, in order that the aqueous vapour may be drawn 

 out of the tube ; this is eflential if we operate in temperatures 

 lower than that of the atmofphere, otherwife not. For want and air dried by 

 of this attention, Col. Roi, in his valuable paper in the Philos. ful P h * acid# 

 Tranf. vol. 67, has been led into fome erroneous conclufions. 

 A fmall column of dry mercury is then let down to a proper 

 point in the manometer, and it is ready for experiment with 

 common air. ' 



It requires fome addrefs to fill the manometer with any other Method of filling 

 gas.— I fucceeded beft as follows : filled the tube with dry the manwneter - 

 mercury ; then puttied down a wire with thread, fo that when 

 the wire was got to the end of the tube, a thick- covering of 

 thread juit entered the open end, and held the mercury like 

 a cork, fo that the tube could be inverted without lofing the 

 contents ; then having a glafs funnel with a perforated cork 

 over the water apparatus, containing the gas, I flipped the 

 manometer through the hole in the cork, and putting my hand 

 into the water under the funnel, drew the wire out of the 

 manometer, and with it the mercury ; upon which the gas 

 entered the manometer. For carbonic acid gas, I opened the Carbonic acid 

 fealed end of the manometer, drew it out to a capillary bore, gas * 

 and forced a ftream of the gas through the tube ; then putting 

 my finger on the other end, fealed it again by a blow-pipe, 

 and let down a fmall column of mercury to the proper point. 



When the manometer was to be expofed to a heat of 212°, Simple method 



I ufed a Florence flafk, with a long glafs tube corked into it, ^applying the 



' ° b » boiling heat, 



in luch fort that as much or the manometer as was necelTary 



to be expofed to the temperature might be in the tube ; then 



the water at the bottom of the flalk was made to boil violently, 



i'o that a conftant ftream of vapour iflued out of the top of 



K2 the 



