62 THE PRACTICAL POULTRY KEEPER. 



atmosphere ; a point further experience has shown to be of 

 much importance, though actual tanks of water are no 

 longer employed. After Mr. Schroder's machine many others 

 were brought forward, and in the United States Mr. Jacob 

 Graves and others constructed elaborate incubators. The 

 principal object with all inventors was to ensure an equable 

 temperature, but few of the ingenious contrivances employed 

 really secured this, and adequate attention was not, as is 

 now known, paid to the proper amount of dampness, or to 

 purity of the atmosphere. 



In 1877 the practice of artificial hatching was revolution- 

 ised by what was termed a "Hydro-Incubator," exhibited by 

 Mr. T. Christy, at the Dairy Show held at the Agricultural 

 Hall, London. This machine was modelled upon one used 

 for some little time previously with success in France, made 

 by Messrs. Roullier and Arnou-lt, 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 off twice in every twenty-four hours, to be 

 replaced by boiling water ; thus keeping up the temperature. 

 When so many had vainly devoted money, pains, and com- 

 plicated apparatus to keep up a regular supply of heat, that 

 a simple machine should succeed which depended altogether 

 upon a re-supply of boiling water every twelve hours, ap- 

 peared to all simply ridiculous. Such, however, proved to 

 be the case. "Hydro-Incubators" were sold literally by 

 hundreds, and were the first to make artificial hatching a 

 practical reality. 



It was some time before it was understood why it was 

 that this success had attended so rude a machine. The 

 secret lay in two points mainly. In the first place, the hot- 

 water tank was very large compared with all other apparatus 

 previously made, holding for a loo-egg machine about 

 twenty or twenty-four gallons. The enormous " specific 



