ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
513 
the capsule, and of thus adjusting the temperature at which the capsule 
shall expand several degrees above that at which it first commenced to 
Fig. 45. 
act. By this means a range of about 8° with any particular capsule is 
obtained. 
Hearson’s Biological Incubator working with a Petroleum Lamp. 
The outer case of this apparatus (fig. 46) is similar to the one 
already described, save only that the woodwork on the right-hand side 
is carried lower down to form a support for the lantern in which the lamp 
T burns. The general construction of the water-jacketed chamber is 
also the same ; but there is a larger water-space below the chamber to 
make room for a pipe L, which leads the heated products from the flame 
through the water and back again to the lantern, the lantern being 
furnished with a second chimney which discharges into the open air 
a short distance behind the one seen in the illustration. A is the water- 
jacket surrounding the chamber containing the cultures. O is the pipe 
through which the water-jacket is filled with water. N is a cock for 
emptying the sime. M is the overflow. S is the capsule contained in 
a case attached by a tube to the lever plate outside. D is a lever pivoted 
on the left, and carrying at its free end a damper F, which when resting 
on the chimney Y effectually closes it. P is a screw for adjusting the 
damper when starting the apparatus. The end of this screw is concave, 
and into this concavity is inserted the upper end of a wire, the lower 
end of which rests on the capsule. H is a lead weight for bringing more 
or less pressure to bear on the capsule. K is the thermometer, the bulb 
of which is inside and the scale outside the heated chamber. The 
apparatus having been adjusted according to the instructions, the action 
is as follows ; — The heated products of combustion, not being able to 
find any exit at the chimney Y, pass along the flue L, and parting with 
the greater portion of their heat en route , return again to the lantern 
by a flue behind and parallel with the one seen in the section, and are 
thence conducted into the open air by a second chimney placed in the 
lantern a short distance behind the one covered by the damper F. 
The products of combustion continue to move in this direction until 
the water and, consequently, the chamber are sufficiently heated to 
distend the capsule. When this point is reached the wire S and P 
will be pushed up by the capsule, and the lever will cause the damper 
to rise more or less off the chimney V. In a short time the damper 
