666 General Notes. 
chamber. This was the form devised several years ago by Profes- 
sor Birge, of Madison, Wisconsin, and because for laboratory 
purposes comparatively few eggs are needed, and principally the 
earlier stages of development, we secure an efficient incubator and 
thermostat ata trifling cost. (Made of sheet-tin, the cost is not 
over five dollars. 
By modifying this form I have made a more elaborate, but more 
convenient, machine, which, having successfully stood the test of 
three seasons’ work at the Johns Hopkins Laboratory, I venture to 
describe. The “drum” was placed in a horizontal position, the 
tube a was added (making A superfluous). Apertures A and R and 
tubes a’ and ¢ were also added, as shown in the figures. The 
“drum ” was supported by a frame similar to what we get by taking 
off the top of a table and turning the rest upside down. The legs 
or uprights at each end were joined by a strip of sheet-iron 2 in. 
wide, forming a saddle-like belt. The forward end-strip, being cut 
six inches wide at its middle point, makes a fire-plate for the flame 
to play on. The point s tends to be the coolest; hence the position 
of the burner. The thermometer ¢ should mark the upper limit of 
the incubation temperature. sheet of tin is hung by wires, 80 
that the Bunsen burner projects through a hole punched in it, and 
thus prevents reflection and loss’ of heat into the surrounding space. 
The whole structure should rest on a plate of zinc if the floor or 
table on which it stands is of wood. A coat of paint on the drum 
reduces radiation and consequent gas-consumption. The eggs are 
placed in pans 2 inches deep by 10 by 16. Each pan is made of 
two similar halves that slip one over the other, like the lid of a 
cardboard box. Thus either side may be up or down, and there- 
fore all the eggs in the pan (forty or more) are turned at once by 
turning the pan, and, besides, the marks on the eggs are easily 
inspected. For ordinary thermostat purposes, the trays can P 
replaced by shelves or drawers. The air circulates in part as indi- 
cated by the arrows, with such an arrangement of the pans as shown 
in the cut, but most of the air passes through the trays directly, 
and, thus, between the eggs. 
If a space be left above the water and the hole h be made to con- 
nect with an aspirator, on the one hand, and the tube A on the other, 
warm, moist air can be forced into the egg-chamber ; but the sponges 
8, 8, are practically sufficient. I found by experience that even 
though the cyclindrical shape is the one giving greatest strength : 
(as well as ease of construction), that zine is not a good material for 
this machine to be made from, as it softens under warmth and yields 
gradually to the pressure. Therefore, if tin be departed from, 
-copper should be chosen ; but, of course, this will raise the priee.— 
J. Nelson. 
