GREENHOUSE AND LABORATORY. 



27 



of the outer corners (lower one in Fig". 2) and have a special 

 pipe to carry the combustion gases out of doors. It can be 

 darkened by a dark hood of cloth, and can be kept running to 

 within two or three degrees of a given point. Of course for 

 some investigation purposes an underground chamber is better, 

 but it seems needless for such work as is here supposed to be 

 carried on.* 



Of the very greatest importance in this course, and, indeed, 

 essential for most physiological work, is a well-ventilated dark- 

 room. This is to be constructed as shown in Figs. 2 and 4. 

 The walls are to be of one thickness of brick on all sides except 

 the laboratory partition, which is to form the fourth side. A 

 space separates it from the outer greenhouse wall in order to 



FIG. 4. SECTION THROUGH PHYSIOLOGICAL DARK-ROOM. 



Scale as in Fig. 2. 



help keep its temperature at that of the greenhouse. It must 

 have two doors, made light-tight by rubber flaps, with a space 

 between them such that a person can enter and close the outer 

 door before opening the inner ; by this arrangement light may 

 never enter. The construction of the roof is important (see 

 Fig. 4). The glass of the greenhouse above it is to be painted 



* Temperature-chambers (thermostats) of all sizes up to rooms, and claimed 

 to lie of great exactness in operation, are a specialty of the firm of Dr. Hermann 

 Rohrbeck, Karlstr. 2O ft , Berlin, X. W. 



