Bo ] 'le's Incub a tor. 
57 
at the top for the special and actual hatching out of the chicks ; but these need no particular 
comment. 1 he special arrangements are more clearly shown in Figs. 35 and 36 . 
Fig. 35 is the regulator. A C is a glass syphon-gauge, connected at B with the heating 
water, heated air, or other medium it is desired to regulate. The water A extends to neariy 
the bottom of the longer leg of the syphon, pressing near the bottom upon the mercury C. 
This is connected by a short piece of vulcanised india-rubber tube, D, with the nearly horizontal 
small glass tube E, which expands at the further end into the larger cup or bowl, F. The mercury 
extends from the point where the expanding water acts upon to the bowl or cup F ; and it 
will be readily understood that as the water expands, and presses on the mercury in the large 
syphon-gauge, it forces a portion along the much smaller tube E, and causes the fluid to rise 
Fig. 34- 
in the cup F. The tube E being some ten or twelve inches in length, the leverage and consequent 
power exerted by the weight of mercury in this cup are very considerable, and fully adequate 
to any operation required for regulating, whatever may be the heating power. The cup F 
is connected by a wire with the lever H K, moving on a fulcrum, I, and is carefully balanced 
by a weight, L. To avoid the too sudden movement which would otherwise occur with the 
least fluctuation of heat (for this regulator is so sensitive as to move with less than the tenth 
of a degree), it is also balanced by a spring, G. 
The superiority of this regulator over previous mercury regulators is, that they depend upon 
the expansion of mercury under heat, whereas this one works by the expansion of water, which 
is many times as great ; while by this expansion acting upon mercury, the greater weight of the 
latter fluid as a motive power is also secured. It is this, combined with the long leverage of 
the tube E, which makes the regulator so delicate. 
So much for the regulator as distinct from its applications. It may be connected with 
