The temperature is the simplest guide to the amount of fermentation taking place, and the uniformity of the temperature in all parts of the mass is desirable, as showing that all parts are fermenting evenly. The cacao is usually shovelled from one box to another every one or two days. The chief object of this operation is to mix the cacao and prevent merely local fermentation. To make mixing easy one ingenious planter uses a cylindrical vessel which can be turned about on its axis. [Illustration: FERMENTING BOXES, JAVA. From the last box the beans are shovelled into the washing basin. (Reproduced from van Hall's _Cocoa_, by permission of Messrs. Macmillan & Co.)] In other places, for example in Java, the boxes are arranged as a series of steps, so that the cacao is transferred with little labour from the higher to the lower. In San Thome the cacao is placed on the plantation direct into trucks, which are covered with plaintain leaves, and run on rails through the plantation right into the fermentary. Some day some enterprising firm will build a fermentary in portable sections easily erected, and with some simple mechanical mixer to replace the present laborious method of turning the beans by manual labour. The general conditions[1] for a good fermentation are: (1) The mass of beans must be kept warm. (2) The mass of beans must be moist, but not sodden. (3) In the later stages there must be sufficient air. (4) The boxes must be kept clean. [1] For full details see the pamphlet by the author on _The Practice of Fermentation in Trinidad_. _Changes during Fermentation._ No entirely satisfactory theory of the changes in cacao due to fermentation has yet been established. It is known that the sugary pulp outside the beans ferments in a similar way to other fruit pulp, save that for a yeast fermentation the temperature rises unusually high (in three days to 47 degrees C.), and also that there are parallel and more important changes in the interior of the bean. The difficulty of establishing a complete theory of fermentation of cacao has not daunted the scientists, for they know that the roses of philosophy are gathered by just those who can grasp the thorniest problems. Success, however, is so far only partial, as can be seen by consulting the best introduction on the subject, the admirable collection of essays on _The Fermentation of Cacao_, edited by H. Hamel Smith. Here the reader will find the valuable contributions of Fickendey, Loew, Nicholls, Preyer, Schulte im Hofe, and Sack. The obvious changes which occur in the breaking down of the fruity exterior of the bean should be carefully distinguished from the subtle changes in the bean itself. Let us consider them separately:--