427 



described in a forthcoming book.* The apparatus for variable-tempera- 

 ture-experiments consisted of five chambers of a type shown in perspective 

 in Fig. 32. The three smaller chambers (C, D, and E), which were 25J/2 

 inches long by 20^ inches wide by -12 inches high, were designed first ; 

 when found to be too small, they were supplemented by two other cham- 

 bers (F and G), which were 39 inches by 20 inches by 48 inches. These 

 smaller chambers were of two kinds: two, (C and D), with glass slides; 

 ane one. (E), with opaque sides. The water tank above chamber D was 

 provided with a glass bottom and glass sides so as to admit skylight 

 through the water. Water from the general supply flowed in through 

 the tank and out through a waste pipe so as to maintain a water level two 

 inches below the top of the water tank. This made it possible to control 

 the supply of cold running water to keep down the temperature of the 

 main chamber on hot summer days. The main chamber was provided 

 with a wooden shelf, as shown in Fig. 32, leaving an opening from below 

 the shelf up into the main body of the chamber when the door was closed. 

 The coils which turned on the heat during the night were under this shelf 

 (ordinarily the sun caused the temperature to rise to about 100° F. on 

 summer days) . To ventilate the cages, the chamber was supplied with 

 humidified air from a compression tank. The wall of the chamber con- 

 tained four small pipes ending in a slender hose-end on the inside and in 

 a small (J-'^-inch) cock on the outside, for the purpose of conducting the 

 atmometer leads, or suction leads, through the wall. The dark chamber 

 (E) was of the same size as the glass-sided chamber and was provided 

 with the water tank above, but received the light only from above, and 

 was intended to demonstrate the efifects of light under the same tempera- 

 ture conditions. Difficulty was usually experienced in maintaining a tem- 

 perature similar to that in the other chambers, which tended to rise higher 

 during the day. The same mean temperature, however, was obtained in 

 this chamber as in the others, although it was done by raising the mini- 

 mum during the period of the night instead of by raising the maxsimum 

 at mid-day. 



The humidifying device which treated the air supplied to these cham- 

 bers, is shown in Fig. 33, consisted of a galvanized-iron cylinder so con- 

 structed as to stand pressure of from five to ten pounds. Air at reduced 

 pressure entered this cylinder at the right. In the top of this cylinder was 

 a Schutte-Koerting head which sprayed cold water into the space through 

 which the air passed, so as to nearly saturate the air at the temperature 

 of the water, which was about 16° C. during the summer months. The 

 surplus water from the humidifying chamber flowed out through a ball- 

 float cock (steam trap — Harding and Willard, '16, p. 214). The air 

 passed over the galvanized-iron cylinder through a condensation separator, 

 which removed any water. This humidifying process supplied air nearly 

 saturated at the temperature of the running water, and the humidity for 

 any temperature above or below this could readily be calculated. This 



* Experimental Animal Ec'ology, to be published in 1927 by Williams & Wilkins 

 Co., Baltimore, Md. 



