Christy's Hydro- Incub a tor. 
59 
was, however, found with the egg arrangements, the pierced plate sliding under the arches 
breaking eggs in work at an alarming rate. This fault, and its costliness, were the chief reasons 
which hindered Mr. Boyle’s incubator from coming into general use. It may be remarked that 
it was found here, again, that when the bottom of the eggs was kept cool, the best temperature 
at the top of the eggs was about io6°, whereas in a warm drawer the best heat is about 103°. 
After Mr. Boyle’s, the only incubator upon the old system that calls for mention was that 
made by Mr. Penman, of Newcastle. In this the bottom of the hot-water tank was formed of 
india-rubber insertion, resting loosely upon the eggs, thus reviving the old plan of Cantelo. It 
was found that after a while the flexible material “ bagged,” when the weight of the water crushed 
the eggs and chickens ; but this could so easily have been avoided, that it seems remarkable no 
attempt has been made to harmonise the top contact system with later discoveries. 
With all these machines eggs had been successfully hatched, and some individuals had been 
able to report as good results as with hens. Mr. Boyle’s, in particular, was particularly successful 
in the hands of a few intelligent people, who “took ” kindly, as it were, to its complicated 
mechanism. But while these succeeded others conspicuously failed ; and artificial hatching was 
not, by any of the machines hitherto described, brought into general practice as a profitable 
method of poultry management. We now have to record the very simple means by which this 
result was first accomplished. 
At the exhibition of poultry in connection with the Dairy Show held at the Agricultural 
Hall, London, in 1877, there was exhibited by Messrs. Christy and Co. what was termed a 
“ Hydro-Incubator.” This machine was modelled upon one used for some little time previously 
with success in France, made by Messrs. Roullier and Arnoult, and it consisted in the main of a 
large hot-water tank over the egg-drawer, of peculiar construction, from which a few gallons of 
water were drawn oft" twice in every twenty- four hours, to be replaced by boiling water ; thus 
keeping up the temperature. The attendant was not, however, able to explain the construction 
of the tank, or the reason for the mode of working ; and the consequence was that not one single 
individual acquainted with the subject — and we were certainly no exception — thought such a 
machine of the least use for practical purposes. That when so many had devoted money, pains, 
and complicated apparatus to keep up a regular supply of heat, a machine should succeed which 
depended altogether upon a re-supply of boiling water every twelve hours, appeared to all simply 
ridiculous. The following year, however, a competition of incubators took place at a poultry- 
show at Hemel Hempstead, at which this incubator far outstripped all competitors ; and the 
success then obtained, so far from being accidental or temporary, was much surpassed on other 
occasions. The earlier machines were in fact somewhat defective in ventilation and other matters ; 
but as improvements were made in these, the simple “ Hydro-Incubators ” were sold literally 
by hundreds, and solved the long-sought problem by making artificial hatching a practical 
reality. 
It took some little time before it was understood clearly, why it was that this success had 
attended so apparently rude a machine. The simplicity might count for something ; but then 
Carbonnier and others had made machines quite as simple which were not generally successful. 
Briefly, however, it may be explained that the whole secret lay in two points mainly, wherein 
the new machine differed from its predecessors. In the first place, the hot-water tank was very 
large compared with all other apparatus previously made, holding for a 100-egg machine about twenty 
or twenty-four gallons. The enormous “ specific heat ” of water makes a large body of it like this veiy 
much more “steady” in temperature than tanks of less content. But much more than this, the 
construction of the tank itself was found to be peculiar, and this was in fact the great excellence 
