HEAT PRODUCTION OF HONEYBEES IN WINTER. 7 



the apparatus may be briefly summarized. The respiration chamber 

 in which the hive was inclosed was ventilated by withdrawing air 

 from the lower portion, passing it through sulphuric acid to remove 

 water vapor and through soda lime to remove carbon dioxid, and 

 returning it to the upper part of the chamber. The increase in the 

 weights of the sulphuric acid and the soda lime during a given 

 period indicates respectively the quantities of water vapor and car- 

 bon dioxid removed from the chamber. These represent the quan- 

 tities produced during the period when due allowance is made for 

 change in the water vapor and carbon-dioxid content of the air as 

 ascertained from analyses made at the beginning and end of the 

 period. Oxygen to replace that removed by the bees was supplied 

 to the chamber from a cylinder, the gas being introduced at a rate 

 sufficient to maintain a certain volume in the system, as indicated by 

 a tension equalizing device which served to keep the air in the cham- 

 ber at the same barometric pressure as that of the laboratory. The 

 quantity of gas admitted was ascertained from the loss in weight of 

 the cylinder or by reading a meter through which the gas was passed. 

 This showed the quantity of oxygen consumed by the bees when cor- 

 rection was made for change in the residual oxygen content of the air 

 of the chamber. In making these corrections for variations in re- 

 sidual gases, changes in temperature and barometric pressure of the 

 air of the system were also taken into account. By proper attention 

 to these means of ventilation, any desired conditions with respect to 

 water vapor, carbon dioxid, or oxygen content of the air could be 

 maintained. 



The temperature of the air surrounding the hive could also be 

 controlled to a certain extent. In a space adjacent to the metal 

 walls of the respiration chamber, and protected by a thick heat- 

 insulating cover, were means for heating and cooling the walls ; also 

 within the chamber was a coil of copper tubing through which cold 

 water could be circulated to take heat from the air about the hive. 

 By weighing the water flowing through this coil and measuring its 

 increase in temperature, the quantity of heat carried out could be 

 ascertained, which, with necessary corrections for heat from other 

 sources, would be that imparted to the air by the bees. 



