The germination of the grain is effected by means of cool moist air provided by the fan described and the cooler and moistener--Figs. 5, 6, and 7, herewith--known as an _echangeur_. As the germinating grain has a depth of from 30 inches to 40 inches some pressure is required, and mechanical means are necessary for efficient and economical turning. The _echangeur_ is a very ingenious application of the well understood rapidity of evaporation of any liquid when spread out in very thin layers over large surfaces and exposed to a current of air. It consists 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.]