288 On Cheese-mahing in Home Dairies and in Factories. 
Gradually filling the floats of this wheel, it at length causes 
half a revolution, which, by crank and lever overhead, actuates 
floating wooden rakes, sinking 2 or 3 inches in the milk, which 
are thus driven a foot or two to and fro upon the surface of the 
milk in the vat, at intervals of a few seconds all night long. 
The evening's milk is in this way cooled before morning, 
even to 60^ or 65° ; and a supply of cool water for this purpose, 
either from a spring or pumped from a tolerably deep well, is 
one of the most important requirements in order to the success, 
of a factory. The object in using the agitating contrivance * is 
to prevent any cream rising on the milk during the night ; but 
it also performs the further important office of doing something 
towards aerating and deodorising the milk — an office which, 
might most beneficially, during the hot weather, be performed 
on the milk before it leaves the farmstead : thus enabling it in 
some measure to get rid of the animal heat and odour which 
tend to the too early and rapid decomposition of the milk in hot 
weather, and are distinctly inimical to the production of the finest- 
flavoured cheese. This aeration should, indeed, take place as 
soon as the milk is drawn from the cow, in which case it may 
be safely taken any reasonable distance, and jolted and shaken 
over any sort of rough and uneven roads, even though contained 
in closely-lidded cans, without fear of its being injured during 
the transit to the factory. Milk obtained from heated cows 
that have been tormented by the attacks of insects during a hot 
summer's day is obviously already in a state of heat and fer- 
ment closely bordering on actual decay. Such milk should be 
well aerated before being despatched. It is not so necessary to 
use these precautions with the morning's milk, which, on arriving 
at the dairy, is at once mixed with the evening's, which has 
been cooled and agitated all night in the milk-vats in the fac- 
tory. When sufficient fresh milk has run into that vat which 
is farthest away from the weighing-machine, the pipe conducting 
the milk from the tin on the weighing-machine, where it is 
received and weighed as it arrives morning and evening from 
the several contributors, is shortened, to adapt it to tlie next vat, 
and so on to the last. Steam is now turned under Vat No. 
and the whole mass of milk in it raised to a temperature of 80' 
Fahr., after which the rennet is mixed with it. Tlie heating oi 
the milk at this stage may with advantage be made to depend a 
little on the state of the weather and the time of the year. In 
hot weather it should not exceed 80^, and in cold it may be as 
high as 82°. The quantity of rennet to be mixed with the milk 
* Another form of this aiiparatns is figured in j\Ir. Willard's paper ou 'Milk- 
condensing Factories,' on page 151, vol. viii., 2ud Series. 
