Hals ted's Incubator . 
the hot water at the circumference, while the return pipe K came from the centre. This was 
to pi event the outer edges of the egg-drawer from being cooler than the middle, a very 
common fault with nearly all incubators then constructed, owing to the shallowness of the 
tanks. Recent improvements have made this ingenious provision of no practical importance. 
Fig- 3i- 
The egg-drawer or nest was constructed of strips of tin or zinc, bent like an inverted V and 
placed thus, AAAA. When using, a woollen blanket or cloth was laid on the strips, dropping down 
between each or every alternate strip, into or just touching the water with which the outer pan of 
the drawer was filled to the depth of a quarter of an inch. This construction was to provide moisture, 
and also to keep the bottom of the eggs cool ; the pan coming in direct contact with the outer air. 
In this manner Mr. Halstcd hoped to get as nearly as possible the same effect as when a hen forms 
her nest on the damp ground, in which case she is almost certain to hatch nine-tenths of her eggs ; 
the A strips also keeping the eggs in rows and preventing them from rolling about. In practice, 
however this actual wet contact was found to spoil and mildew the eggs , and aftci much time had 
been lost in finding out the cause of this, it had to be abandoned. 
The regulator was a glass tube of about three-eighths or half an inch in diameter and eight 
inches long, having at one end a bowl holding half a pound of mercury. As the mercury 
<JT\ 
