1844.] of Bodies generally existing as Gases. 97 



they passed, in their way from the air-holder to the pump, 

 through a coil of thin glass tube retained in a vessel filled with 

 a good mixture of ice and salt, and therefore at the tempera- 

 ture of Fahr. ; the water that was condensed here was all 

 deposited in the first two inches of the coil. 



The condensing tubes were of green bottle glass, Fig. 1. 

 being from ^th to ^th of an inch external diameter, 

 and from ^nd to y^th of an inch in thickness. 

 They were chiefly of two kinds, about 11 and 9 

 inches in length ; the one, when horizontal, having 

 a curve downward near one end to dip into a cold 

 bath, and the other, being in form like an inverted 

 siphon, could have the bend cooled also in the 

 same manner when necessary. Into the straight 

 part of the horizontal tube, and the longest leg of 

 the siphon tube, pressure-gauges were introduced 

 when required. 



Caps, stopcocks and connecting pieces were 

 employed to attach the glass tubes to the pumps, 

 and these, being of brass, were of the usual character of those 

 employed for operations with gas, except that they were small 

 and carefully made. The caps were of such size that the ends 



Fig. 2. 



of the glass tubes entered freely into them, and had rings or a 

 female screw worm cut in the interior, against which the cement 

 was to adhere. The ends of the glass tubes were roughened 

 by a file, and when a cap was to be fastened on, both it and 

 the end of the tube were made so warm, that the cement *, 

 when applied, was thoroughly melted in contact with these 

 parts, before the tube and cap were brought together and 

 finally adjusted to each other. These junctions bore a press- 

 ure of thirty, forty, and fifty atmospheres, with only one 

 failure in above one hundred instances ; and that produced no 

 complete separation of parts, but simply a small leak. 



The caps, stopcocks, and connectors, screwed one into the 



* Five parts of resin, one part of yellow bees'-wax, and one part of red 

 ochre, by weight, melted together. 



H 



