1 62 A RESPIRATION CALORIMETER. 



at all comparable with the precision obtainable in weighing with the 

 system just described. Arrangements were accordingly devised so that 

 the absorbers could be weighed by this system. 



The bulk of the weight of the absorbing system is borne by three 

 equipoises, one of which is shown in figure 33. These three points of 

 support prevent any great lateral motion of the system. The system 

 is suspended by attaching eighth-inch iron pipe (3 mm. internal diam- 

 ter) to the pipes in the hanger and thence to the absorbing system. A 

 piece of stout copper wire was wound about the upper coil of pipe in 

 the absorbing system at the rear of the chamber so as to form a 

 loop. The 3 mm. pipe was slipped through one end of this loop and 

 the other end into the pipe of the hanger. Two similar loops of stout 

 copper wire were attached to the absorbing system near the front on 

 both sides about 42 cm. from the corner. A long T was then made of 

 three pieces of the 3 mm. pipe, the two arms of theTwere slipped through 

 these copper loops, and the stem of the T inserted in the pipe in one arm 

 of the cross or hanger. When the shields were lowened to such a point 

 that their weight rested on the copper disks, the lead counterpoises were 

 raised from their position and the whole system became suspended on 

 the central suspension rod of the weighing system. Owing to varia- 

 tions in the amount of water condensed on the surface of the different 

 portions of the absorbing system, it became necessary to balance the 

 system in such a manner that the three lead counterpoises and equal 

 beams should be in an approximately level position and clear of the 

 absorbing system. This balancing was done by shifting two lead weights 

 provided with hooks in the top, which could be hung on the 3 mm. pipe 

 used to support the absorbing system. After a little practice the subject 

 could slide the weights along these pipes and bring the whole system 

 into equilibrium very rapidly. When in equilibrium an observer out- 

 side signaled the assistants stationed at the balance overhead and the 

 weighing was made. 



Owing to the multiplicity of bearings of the three equipoises, the 

 degree of accuracy obtained when weighing the man was not to be ex- 

 pected. It was found, however, that when the adjustments were prop- 

 erly made, differences in weight of the absorbing system of i or 2 grams 

 could be accurately determined. Thus we have a method for noting 

 changes in weight of the absorbing system that is as accurate as could 

 be desired, for it is more than probable that the amount of moisture 

 condensed on the surface of the calorimeter, the bicycle ergometer, the 

 telephone, connecting wires, etc., sometimes amounts to i or 2 grams, 

 and hence weighings closer than this would have no significance. 



