of a cylinder, or series of cylinders, of increasing diameter, placed
one within another. Each consists of finely perforated sheet iron. They
are placed in a trough of water, just sufficiently immersed to insure
complete wetting. When rotated at a slow speed, the surfaces of all the
cylinders are kept just wetted. A volume of air is either driven or
drawn through, as may be required for any particular purpose. In the
model malting, as shown at Fig. 4, taken from that shown at the Brewery
Exhibition, the air was driven through the _echangeur_ and thence
through the germinating barley. Here or as employed in the malting
illustrated, the air in its passage comes first into contact with the
moistened cylinders, and if hot and dry it becomes moist and cool, for
the constant evaporation upon the cylinders has a very considerable
refrigerating effect.

This was well known to the Egyptians over four thousand years ago, and
the porous bottle--_gergeleh_--of Esnch has been made until the present
day, to keep the drinking water cool and fresh. The _echangeur_ is
like a gigantic gergeleh, and by increasing the size and number of the
cylinders, and causing the water in the moistening trough to circulate,
any volume of air can be wetted to the saturation limit corresponding to
its temperature. It will be seen that this apparatus gives the maltster
complete control of the humidity and heat as well as volume of the air
driven through germinating corn.

[Illustration: Fig. 8.]

The turning apparatus is shown by Fig. 4, and consists, as will be seen,
of a cylindrical frame provided with rollers which run on rails at the
edge of the germinating cases. It is carried to and fro from either end
of the case by compensating rope gearing which at the same time gives