GAS-METER. 127 



produce an oscillation or " jump." In a station-meter the intervention of the 

 gasometer will remedy this defect. A variation in the arrangement of the 

 drum, therefore, is a matter of necessity. The station-meter is formed for 

 strength and durability, the way in which its drum is put together being more 

 mechanical than that of the consumer's meter. 



I have stated that the construction of the drum of the consumer's meter 

 differs of necessity from that of the station-meter : it is so when the drum of 

 the latter is made in the forms given in Plate XV. Station-meters are, how- 

 ever, sometimes made with drums like the smaller kind, but the measure will 

 vary with every change in the water-line. If it is too high, the quantity 

 marked will be too little ; if too low, the quantity marked will be too great ; 

 these are circumstances to which the station-meter ought not to be liable, 

 and which the form shown in the Plate completely obviates. 



By referring to the annexed figures the construction will be understood. 



Fig. 28. 



As in the former case, the outer circumference or rim of the drum is divided 

 into four partitions, separated from each other by partition-plates, not run- 

 ning across directly at right angles with the face, but beveling from the plane 

 of the water, meeting the wrap of the opposite hood. The sides of these par- 

 titions are also beveled ; the space left between each plate forming, on one 

 side of the drum, the inlet, and on the other side the outlet for the gas ; the 



