GAS SAMPLER. 



is drawn out by the tube h, and this should be so regulated 

 by the cock d that only from ^^- to -g-J-g- is collected. 



Whenever the level of the mercury lowers, it shows a 



FIG. 30. GAS SAMPLER. 



clogging in the slot, and it should be cleaned by moving the 

 rod. This always indicates when cleaning is necessary, and 

 it sometimes keeps clean for hours. 



When a sufficient sample has been obtained turn up the 

 tube d, and then the gas-holder can be carried away. 



The method recommended by the American Society of 

 Mechanical Engineers is to have a "box or block of gal- 

 vanized sheet iron equal in thickness to one course of brick," 

 and secure in it a series of J-inch gas-pipes, all alike at the 

 ends and of equal lengths, in such manner that the open ends 

 may be evenly distributed over the area of the flue A (Fig. 

 32), and their other open ends enclosed in the receiver B. 



