1 3 o 



A RESPIRATION CALORIMETER. 



almost touches the projection on the upper side of the lower compart- 

 ment on the other can, will be moved upward, and at the same time a 

 projection attached to the bottom of the can will accomplish the closing 

 of the valve on the other can. 



In order that the force required to open and close the valves may 

 not interrupt the descent of the can and interfere with the proper 

 weighing of the water, an arrangement for increasing the momentum 

 of the full can is provided. This device is illustrated in figure 36. 



The rod on which the counterpoise is suspended from the beam is 

 tipped on the lower end with a small bulb which opens the jaws of a 

 spring clutch, a. By means of a small nut with a right and left hand 

 thread the tension of the spring may be varied at will, and is so 

 adjusted that a pull of about 200 grams is necessary to release the bulb. 



FIG. 36. Clutch to regulate tension on Water-Meter. Two curved steel springs hold a 

 bulb on the end of a steel rod at bottom of lead counterpoise of the water-meter. 



When the tension of the clutch has been overcome the bulb is released 

 rather suddenly, and as it passes through the jaws of the clutch, these 

 snap together, and their converging ends, rubbing on the bulb, give a 

 distinct impetus to the upward movement of the counterpoise, thereby 

 imparting momentum to the whole system. By this means sufficient 

 force is obtained to operate the valves ; indeed, the end of the beam 

 that bears the cans is invariably forced to a position below the level, and 

 the pointer on the spring balance travels much farther than the true 

 weight would warrant. The spring in the balance, however, soon im- 

 parts a movement in the opposite direction. This reverse movement of 

 the spring aids materially in the use of the balance, for by its means 

 the balance-beam is drawn a little distance away from the wire projection 

 used to deflect the water current, and the ends of the levers on the 

 valves are slightly removed from the projections on the cans, and thus 

 the whole system is freely suspended. Inasmuch as about 20 seconds 

 elapse in the passage of the water from the upper chamber to the lower 



