566 



GAS, COAL 



same operation is performed at the opposite extremity of the tube d, which is thus 

 hermetically sealed, and assumes the appearance shown \nfig. 1023. 



1021 



1023 



1022 



The gas having been thus carefully collected, the necessary analytical operations 

 must be conducted over mercury in a small wooden pneumatic trough, with plate- 

 glass sides, the construction of which is shown in fig. 1024. A is a piece of hard well- 



1024 



seasoned wood, 12 inches long and 3 inches broad, hollowed out, as shown in the 

 figure; the cavity is 8j inches long, 1^ inch broad, and l inch deep. The bottom 

 of this cavity is rounded, with the exception of a portion at one end, where a surfaco, 

 1 inch broad, and 1 inch long, is made perfectly flat, a piece of vulcanised India- 

 rubber, -j 5 th of an inch thick, being firmly rrmrntcd upon it. Two end pieces, n n, : jths 

 of an inch thick, 3 inches broad, and fi inches high, are fixed to the block A ; these 

 serve below as supports for A, and above as tho cuds of a wider trough, which is 

 formed by tho pieces of plate glass c c, cemented into A and n n. Tho ^lass plates 

 c c, are 10.} inches long, and l inch high ; they are slightly inclined, .-<> that their 

 lower edges are about 2| inches, and their upper edges 2 inches apart. This trough 

 stands upon a wooden slab D D, upon which it is hold in its place by two strips of 

 woodee. An upright column F, which is screwed into D, carries tho inclined stand 

 o, which serves to support tho eudiometer during tho transference of gas. A is a 

 circular inclined slot in B, which allows of tho convenient inclination of tho eudio- 



