fallen tree in his forests; but in the same way attack the timber which he wishes to preserve, especially if it is kept in a moist condition.  Thus they contribute largely to the gradual destruction of wooden structures.  It is therefore the presence of these organisms which forces him to dry his hay, to smoke his hams, to corn his beef, to keep his fruits and vegetables cool and prevent skin bruises, to ice his dairy, to protect his timber from rain, to use stone instead of wooden foundations for buildings, etc.  In general, when the farmer desires to get rid of any organic refuse, he depends upon bacteria, for they are his sole agents (aside from fire) for the final destruction of organic matter.  When he wishes to convert waste organic refuse into fertilizing material, he uses the bacteria of his compost heap.  On the other hand, whenever he desires to preserve organic material, the bacteria are the enemies against which he must carefully guard.

Thus the farmer’s life from year’s end to year’s end is in most intimate association with bacteria.  Upon them he depends to insure the continued fertility of his soil and the constant continued production of good crops.  Upon them he depends to turn into plant food all the organic refuse from his house or from his barn.  Upon them he depends to replenish his stock of nitrogen.  It is these organisms which furnish his dairy with its butter flavours and with the taste of its cheese.  But, on the other hand, against them he must be constantly alert.  All his food products must be protected from their ravages.  A successful farmer’s life, then, largely resolves itself into a skilful management of bacterial activity.  To aid them in destroying or decomposing everything which he does not desire to preserve, and to prevent their destroying the organic material which he wishes to keep for future use, is the object of a considerable portion of farm labour; and the most successful farmer to-day, and we believe the most successful farmer of the future, is the one who most intelligently and skilfully manipulates these gigantic forces furnished him by the growth of his microscopical allies.

Relation of bacteria to coal.  Another one of Nature’s processes in which bacteria have played an important part is in the formation of coal.  It is unnecessary to emphasize the importance of coal in modern civilization.  Aside from its use as fuel, upon which civilization is dependent, coal is a source of an endless variety of valuable products.  It is the source of our illuminating gas, and ammonia is one of the products of the gas manufacture.  From the coal also comes coal tar, the material from which such a long series of valuable materials, as aniline colours, carbolic acid, etc, is derived.  The list of products which we owe to coal is very long, and the value of this material is hardly to be overrated.  In the preparation of these ingredients from coal bacteria do not play any part.  Most of them are derived by means of distillation.  But when asked for the agents which have given us the coal of the coal beds, we shall find that here, too, we owe a great debt to bacteria.