128 Report of the Department of Bacteriology of the 



of brass is to keep down fungus growth within the pipe, not so much 

 because of the toxic action of the brass itself, as because 'copper 

 sulphate can be added at intervals without causing electrolytic 

 action. 



In each of the incubators steel bars were used to support the 

 upper layers of cork. Strips of wood impregnated with paraffin, 

 however, having lower conductivity to heat, would undoubtedly 

 have caused less heat transference from chamber to chamber. 



Hinges and door clasps were of brass. 



Miscellaneous materials. — Between the oak casing and the cork- 

 board of both refrigerator and incubators was laid the best obtain- 

 able quality of building paper. 



In the incubators a Nonpareil Finishing Cement 3 was applied 

 directly to the inner surface of the cork. The cement was covered 

 with three coats of paint to secure a harder and more waterproof 

 surface. This cement was used, instead of ordinary Portland cement, 

 because it was understood to be less liable to crack. In the 37° 

 incubator, however, cracks have formed; and as this cement sets 

 slowly and never becomes very hard, its use is hardly to be recom- 

 mended. 



CONSTRUCTION. 



The dimensions and main details of construction of the refriger- 

 ator and incubators are shown in Figs. 2-4. Fig. 2 is a front 

 elevation, while Figs. 3 and 4 are sections to show the construction 

 in detail. The present description is merely supplementary to these 

 figures. 



Construction of refrigerator. — The refrigerator is 35x40x81 

 inches over all and has a capacity of 25 cu. ft. These dimensions 

 are not ideal, but were determined by the space available. Had 

 space permitted, a broader ice-chamber, which could better accommo- 

 date an ordinary cake of ice, would have been more satisfactory. 



In order to secure rigidity the outer case of oak was built with 

 box headings at the top and bottom, as shown in Fig. 3, carefully 

 breaking all the joints and laying the battens in fresh paint. Inside 

 these headings, after building paper had been tacked over the oak, 

 the four-inch layer of cork was fitted snugly into place. The head- 

 ings were then covered with matched pine. The building paper 

 and cork-board were next fitted closely around the back and sides. 

 This layer of cork was covered in turn with seven-eighths-inch 

 white pine. The resulting box, 23x28x69 inches, was lined with 

 heavy zinc, the angles flushed with solder, and the front edge of 

 the zinc nailed closely to the front edge of the pine lining. 



To support the drip-pan and the ice-rack which lies in it, a wooden 

 shelf was built 20 inches from the top of the chamber. In front 



3 Nonpareil High Pressure Finishing Cement, obtained of Armstrong Cork Co. 



