RESTING TRAVELLED EGGS. 85 



therefore, it lifts p and F. If the machine were started thus, 

 the heat would therefore rise to 98, and at this point the 

 valve P would open. But the sliding weight H allows more 

 pressure to be put upon the capsule, which has the effect of 

 raising the boiling-point (the boiling-point of water rises about 

 l for every inch pressure of the barometer). In this way, 

 therefore, the boiling-point may be set anywhere from 98 Q to 

 107, and will afterwards, whatever the variations in outside 

 temperature, keep the heat regular within about two degrees. 

 The only exception would be in any unusually high situation, 

 which, owing to the less barometrical pressure, would require 

 an ether prepared accordingly; and in several instances this 

 has been found to be the case, but a special capsule has at once 

 removed the difficulty. From numerous sources we learn that 

 the incubator thus designed and regulated has hatched with 

 almost unvarying regularity and success. 



Such are the most successful incubators lately constructed, 

 and only a few general remarks need be added. In artificial 

 hatching, it is of great importance that the eggs Refresh. The 

 earlier incubators rarely hatched any eggs laid more than three 

 days before putting in the machine. The modern ones here 

 described have often reported successful hatches of eggs laid a 

 fortnight before, and which have also travelled by rail ; and no 

 greater proof can be given of the Advance attained. But every 

 pains should be taken to give the machine a fair chance in this 

 respect; and one modern discovery should receive special 

 attention, though of importance to all poultry-keepers. The 

 risks of " tra veiled " eggs, and their uncertainty of result, are 

 well known. But it has been recently established by careful 

 experiments, often repeated, that if after a journey one-half the 

 eggs be " set " at once under a hen, while the rest are kept still 

 and free from jar for twenty-four hours, on an average tlwse kepi 

 hatch much the best. It appears that even the undeveloped 

 gevm, by virtue of the principle of life implanted in it, has 



