126 A RESPIRATION CALORIMETER. 



will go, the incoming water is cooled to as near zero as possible, and 

 the rate of flow through the absorbing system is at the maximum. 

 Indeed, in one series of experiments with a professional athlete a third 

 pipe with disks was suspended above the absorber system, thus increas- 

 ing the heat-absorbing area by 50 per cent. 



It is thus seen that the heat-absorbing capacity of this form of ab- 

 sorber can be varied within very wide limits. It is possible to vary 

 the rate of heat absorption with this apparatus so as to bring away as 

 low as 40 calories per hour and as high as 600 calories per hour. Both 

 of these measurements being irrespective of the amount of heat required 

 to vaporize the water vapor issuing in the air current, they indicate the 

 heat-absorbing capacity of this form of absorber rather than the heat- 

 measuring capacity of the calorimeter. 



Besides serving to increase and diminish the effective surface of the 

 absorbing system, these troughs and the gutters attached to them serve 

 also the important purpose of collecting the large quantity of water 

 which condenses on the surface of the absorbers and the shields, as 

 explained on page 23. 



SUPPLY OF WATER FOR MEASURING HEAT. 



A regular pressure of water in the absorber pipe is quite essential. 

 Owing to the marked fluctuations in the city water pressure, the water 

 flowing through the heat-absorber system is taken from a tank in the 

 second story of the building 10 meters above the point at which it 

 enters the calorimeter. A constant-level attachment on the tank gives 

 a steady pressure and flow of water. 



WATER COOLERS. 



The temperature of the water entering the calorimeter is regulated 

 according to the amount of heat to be brought away, and may vary 

 from i to 12. In order to secure such variation, provision is made 

 for directing a portion of the water through two coils of iron pipe in 

 tanks that can be filled with crushed ice. These tanks are placed in a 

 small unheated room adjoining the calorimeter laboratory. Two valves 

 near the calorimeter provide a means for mixing the cooled water and 

 the water direct from the supply tank in whatever proportions are de- 

 sired. A system of pipes and valves makes it possible to use either 

 one or both cooling tanks at will. 



WATER METER. 



To determine the quantity of heat brought out of the chamber it is 

 necessary to measure accurately the quantity of water that flows 

 through the absorber. Formerly the measurement of water was made 



