THE SOIL.                       19
fruits and vegetables for a series of years, without manure and with only indifferent ploughing. The ability of the clay sub-soil to retain moisture explains, to some extent, the enduring quality of the land. The bottoms are mainly covered with a deciduous growth of vinemaple, alder, crab-apple and salal-berry, with only occasional firs and pines, and, as a rule, are confined to narrow valleys. Unlike prairie-lands, they must be cleared, at a cost varying from $15 to $20 per acre, before they can be ploughed. Usually, however, the wood and lumber thus secured will pay for the work, and the farmer will afterwards find his reward in the abundance of his crops.
The soil of the up-lands is somewhat inferior to that of the riverbottoms. That of the undulating foot-hills and more tillable mountain faces is red, brown or black loam. The more elevated lands afford excellent natural pasturage and also produce good crops of grain and the hardier fruits and vegetables.
East of the Cascade Mountains, the soil is a dark loam of great depth, composed of alluvial deposits and decomposed lava overlying a clay sub-soil. This, in turn, rests upon a basaltic formation which is so. far below the surface of the ground as to be visible only on the banks of'the deep water-courses. The constituents of this soil adapt the land peculiarly to the production of wheat. All the mineral salts which are necessary to the perfect growth of this cereal are abundant, reproducing themselves constantly as the processes of gradual decomposition in this soil of volcanic origin proceed. The clods are easily broken by the plough, and the ground quickly crumbles on exposure to the atmosphere. Although the dry season continues for months, this light porous land retains and absorbs enough moisture from the atmosphere, after its particles have been partially disintegrated, to insure perfect growths and full harvests. This assertion is so at variance with common experience that it might well be questioned. Happily, it is susceptible of explanation. In spite of the fact that there is scarcely a shower between May and the following October, and that the average rainfall for the year does not exceed 20 inches, there is always the requisite moisture for maturing the crops. Paradoxical as it may seem, if the rain were greatly in excess of this low average, damage would certainly ensue; and it is equally sure, if successful farming depended upon the limited rainfall, there would be poor harvests. The clouds supply only in part the moisture which is needed. The warm air-currents, surcharged with vapor, which sweep inland from the ocean up the channel of the Columbia River prevent drought. The effect of these atmospheric currents in tempering the climate has already been described.  Their influence upon the vegetation is no less vital. The moisture with which they are