THE CALORIMETER SYSTEM AND MEASUREMENT OF HEAT. 129 



the lower end of which is in this cup-shaped vessel. By swinging 

 this pipe through a small arc the current of water is deflected to either 

 side of the partition in the receiving cup and directed through the 

 bent tubes into either can. This pipe is moved to one side or the other 

 by means of wire projections, W, extending below the arms of the 

 balance-beams. When one can is full of water and sinks, the falling 

 end of the beam pushes against the wire and moves the outlet pipe so 

 that the water current is deflected to the opposite side of the receiving 

 cup, from which it flows into the empty can. 



As the full can sinks, a valve in the outlet pipe is opened and the 

 water drains into a smaller can, D, below. While this is filling there 

 is no loss in weight, but as soon as it is full the water begins to flow 

 away through a siphon, and also through an overflow pipe. As is 

 seen from the construction in the drawing, the small can is provided 

 with two openings, one of which, the overflow C, is made by soldering 

 a piece of pipe into the bottom of the small can in such a manner that the 

 upper end of the pipe nearly touches the top of the can. A small siphon 

 attached to a nut, F, screwed into the bottom of the can is the second 

 opening. As soon as the small can is filled the siphon is started. As 

 the diameter of the siphon tube is very much less than that of the 

 opening through the valve, the lower chamber fills up to the level of 

 the overflow C, and water soon begins to flow out of this opening. 

 As soon as all the water has passed out of the upper can, the overflow 

 through the large tube ceases and the lower can is completely emptied 

 by means of the siphon. The end of the short arm of the siphon nearly 

 touches the bottom of the small depression in the cap F, into which 

 all the water from the can drains. It is thus seen that the lower cham- 

 ber is constructed on the principle of the Tantalus cup. It has been 

 found by repeated experiment that the quantity of water adhering to 

 the walls of both the upper and the lower cans is remarkably constant. 



The valves in the outlets to the large cans are opened or closed au- 

 tomatically, as the balance-arm assumes a level position. The valve 

 on each can has a long lever, the end of which is between the upper 

 and lower compartments of the other can, and is moved upward or 

 downward with the motion of the can. This construction is seen in 

 figure 35. Thus, as one of the cans sinks, the effect is to open the valve 

 at the bottom of the moving can and to close the valve at the bottom 

 of the stationary can. 



In figure 35 the water is shown as entering the right-hand can. 

 The valve between the upper and lower can is represented as being 

 closed. If, now, this can settles, the water will be deflected to the 

 other side of the receiving chamber, the handle of the valve, which 



9 B 



