THE CALORIMETER SYSTEM AND MEASUREMENT OF HEAT. 159 



In weighing any suspended object, some up-and-down motion is of 

 course necessary. If an equipoise were used, this motion would extend 

 through several inches, but if a platform 

 balance is used, it may be cut down to a 

 small fraction of an inch. Moreover, a 

 series of tests showed that if all lateral 

 motion could be eliminated it was pos- 

 sible to remove the hooks fastened to the 

 under side of the platform and designed 

 to prevent lateral motion and thus ma- 

 terially increase the sensitiveness of the 

 balance. 



The balance in use is of the Fairbanks 

 platform type, designated by the manu- 

 facturers as a silk platform scale. It is 

 graduated to 10 grams and has a capacity 

 of 150 kg. It was put in place exactly 

 over the opening through the floor down 

 into the calorimeter, carefully leveled by 

 placing thin strips of copper under each 

 of the corners, and was rigidly fixed in 

 this position. A hanger was constructed 

 of half-inch pipe, and a quarter-inch rod 

 attached to the lower part of the hanger 

 extended through the opening into the 

 calorimeter. On the lower end of this rod 

 was attached a rubber stopper for closing 

 the opening when the weighing is com- 

 pleted, and a stout iron ring into which 

 various supports for weighing the man 

 and other objects could be hooked. The 

 adjustment of the balance and this tube 

 were such that the rod swung freely, and 

 even with considerable vibration on the 

 lower end would not touch the sides of 

 the tube. 



The same conditions affecting the open- 

 ing through the food aperture as regards 

 necessity for preventing leakage of heat 

 or air obtained in making this opening 

 through the calorimeter chamber. The 

 leakage of heat was prevented by using 



FIG. 46. Weighing Apparatus for Ob- 

 jects Inside the Chamber. A chair is 

 suspended on a rod extending from 

 top of calorimeter chamber. A metal 

 yoke is hung over the platform of bal- 

 ance, so that chair and subject can 

 be weighed directly. A rubber dia- 

 phragm prevents escape of air. 



