Microscopy. 665 
view of supporting frame, 5; natural size—other figures, ṣẹ natu- 
ral size. Explanation of letters: a, inhalent air-tube, 1 in. diame- 
ter; a’, exhalent air-tube; B, block supporting Bunsen burner ; 
b, b, braces holding interior drum against upward pressure of the 
water; c, cover fitting into the end of interior drum or brood- 
chamber ; c’ (placed near lower end of handle of cover), cork-stopper 
fitting into a thermometer-hole through the cover; F, upright pieces 
of supporting frame; F’, F”, side and end base-boards of support- 
ing frame; f, fire-plate, portion of f the supporting belt; G, glass 
Figl Fig 3 
te tk ER 
KAY Z 4 © © © 
Fe] (ofan Bs 
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frame covered by sheets of tin; v, space below foot-boards for 
ingress of air, tubing, ete. The tube A is not essential, but may be 
convenient at times, as seen below. 
, +he structure is essentially a water-jacketed bucket, made by fit- 
ting a smaller cylinder or drum 16x19 in. inside a larger drum 20 
in. In diameter by 24 in depth, thus leaving the space shaded in the 
cut for water. The cover has a double wall with air space (dotted 
in Fig. 1). It slips into its place like the cover of a tin pail. With 
only the tube A, and properly supported in the upright position, 
the gas-flame burning at g, the hole c’ open, and a regulator at H, 
we have the essentials of a laboratory incubator. The air passing 
through the tube—surrounded by warm water for a considerable 
tance—is so warmed as not to chill the eggs placed in the brood- 
