inside with felt. The inside margin of the door is provided with a pro- 

 jection (fig. 2, c) which fits snugly into a felt-lined groove (fig. 2, fc), 

 extending around the front side of the chamber. The door is 3 inches 

 shorter than the front of the chamber, the remaining space being closed 

 with copper and provided with a ventilator (fig. 1, h) which permits the 

 exit of carbon dioxid, and can be closed tigbtly with a slide. Perfect 

 closing of the door is farther effected by a copper slide extending along 

 the front margin, which catches firmly at the top and bottom of the 

 chamber (fig. 2, d d). This device, together with the groove and its 

 corresponding projection, are adapted from the Rohrbeck bacteriological 

 chamber. The outside door is furnished with a frame into which slide 

 two plates of galvanized iron painted dead black inside and covered 

 with felt (fig. 1, i j). By this arrangement the interior of the chamber 

 may be kept dark or exposed to light, or, if desired, one-half may be 

 dark and the rest light, the other conditions remaining the same. By 



raising these slides the thermometers 

 can be read without opening the door. 

 Glass plates of various colors may be 

 substituted for the slides if the effects 

 of different rays of light on plant growth 

 are to be studied. 



Seven movable shelves, placed 2J 

 inches apart, are held in place by cop- 

 per ledges one-quarter inch wide. These 

 shelves are made of galvanized iron 

 rods 1 inches apart, and each one is 

 capable of holding up 60 pounds weight. 

 The temperature is controlled by a 

 low-temperature thermoregulator (fig. 

 1, 7;). A very low and equable flame is 

 secured with a micro-bunsen burner 

 (fig. 1, e). One of the openings into the 

 water jacket (fig. 1, d) is 2 inches in diameter to admit a Roux thermo- 

 regulator, if a very even temperature is desired, as in bacteriological 

 work. Fresh air or different gases can be forced into the chamber at 

 one of the openings at the top (fig. 1, c c) and out at the bottom (fig. 1, /). 

 Each of the openings at the end (fig. !,/#) is closed with a screw cap. 

 The chamber is provided with three tin-lined copper pans, each hav- 

 ing a narrow ledge around the inside near the top, which serve to hold 

 copper rods with folds of cloth, if the experimenter wishes to test seeds 

 according to the Geneva pan method. The pans also serve to hold 

 porous saucers or plates. 



The chamber when empty weighs about 100 pounds, and is therefore 

 easily moved. The shelves will hold about sixty blotter tests, with an 

 equal number of duplicates. It rests upon a detachable base consisting 

 of a stout iron frame 15 inches high, inclosed with a sheet-iron jacket. 



FlG. 2 One-half of door (inside view) : a a, 



hooks for holding thermometer; 6, sec- 

 tion of groove in chamber into which fits 

 c, projection on door ; d d, door fastener. 



