218 
WISCONSIN STATE AGRICULTURAL SOCIETY, 
The ordinary heater is constructed separately from the vat, 
and consists of wrought-iron pipes, screwed together in such a 
manner as to form a fire-chamber, and present a large amount 
of heated surface. 
Fig. 11 .— View of Millar’s Heater, with Front and Side of Brickwork removed. 
When a boiler and engine are used, power is afforded for 
driving the churns, and in this respect this system must prove 
most convenient. Still as the expense is considerably more 
than for the self-heater, both in the first cost and for fuel, many 
prefer the latter. We give figures of two kinds of heaters 
that are very largely in use. 
