POPULAR SCIENCE MONTHLY. 



'caught on' to the surreptitious use of gas ranges are either the fortunate 

 possessors of 'slow' meters or are deluding themselves as to the amount 

 of gas which they actually consume. 



Fig. 4 is a photograph of the common dry meter, with the front, 

 back, top and left side removed. It is called a 'dry' meter to dis- 

 tinguish it from those meters, having little vogue in this country, 

 which employ a liquid in place of a valve motion. The apparatus 

 shown consists of a case divided into three compartments by a horizon- 

 tal partition one fourth of the way down from the top, and by a 

 vertical partition centrally placed and extending upward from the 

 bottom of the casing to the horizontal partition. The upper com- 

 partment contains the registering mechanism and a small valve cham- 

 ber, the latter corresponding to the steam chest of an engine. In each 

 of the lower compartments is a metal disk attached to the central 

 partition by well-oiled flexible leathers, each disk, leather and the 



partition forming a bellows. As in a locomotive, the meter really 

 consists of two separate mechanisms, set to operate out of phase and 

 avoid dead centers. 



Considering one mechanism only, recourse may be had to a dia- 

 grammatic representation of the action (Fig. 5). Gas entering the 

 inlet passes into the valve chamber. Here an ordinary D-slide-valve 

 closes two of the openings, leaving a third through which the gas may 

 flow into the bellows or inner compartment. The bellows expands, 

 gradually filling the outer compartment, and forcing the gas out under 

 the valve into the outlet pipe, as indicated by the arrows. When 

 the bellows is fully distended the valve shifts into the position shown 

 in Fig. 6, admitting the inflowing gas to the outer compartment and 

 collapsing the bellows, whose contents are forced into the outlet pipe 

 by the paths traced by the arrows. 



Thus, it will be observed, the meter is a volume measurer pure and 



