196 POULTRY BREEDING 
that it would hatch all but 2 per cent of the perfect eggs. 
This shows that the incubator manufacturers of these 
days have some precedent for the claims they make as to 
the hatching qualities of their machines. These early in- 
cubators seem not to have created any permanent impres- 
sion, as did the first reaping machine, as there is no direct 
line of descent from them to the incubators of the present 
day. 
A Mr. Halstead, who was a well-known poultry 
breeder 50 years ago, invented an incubator known as 
the “Model,” which was a hot-air machine. James Ran- 
kin, the originator of the modern system of raising ducks 
in large numbers, invented a hot-water incubator some- 
time in the 70's of the last century, and a Mr. Campbell 
of Pennsylvania put out a machine of the hot-water type 
a little later. Mr. Campbell’s machine was called the 
“Eureka.” It had a clock-work attachment to turn the 
eggs at regular intervals and an electric alarm to denote 
when the temperature became too high. Mr. Halstead’s 
machine had an ingenious regulating device that operated 
by the expansion of air in a cylinder, and Mr. Rankin first 
used the expansion of water in the tank to regulate the 
temperature. As none of these machines survived for a 
very long period, it is evident that they lacked in the 
essentials that make for success. 
Later numerous inventors turned their attention to in- 
cubation, and a large number of machines of this kind 
were offered, many of them being crude and unscientific, 
although they were sold in large numbers. 
There are now two types of machines on the market. 
One heats the egg-chamber with currents of hot-air or 
by the radiation of hot-air, and the other heats the egg- 
chamber by means of hot-water in a tank above the eggs. 
