These are but hasty suggestions of methods which will doubtless be multiplied, varied, and improved upon, in the light of future experience and study. And when the very best and most effective methods of subduing the Plains to the uses of civilized man shall have been discovered and adopted, there will still remain vast areas as free commons for the herdsmen and sporting-grounds for the hunter of the Elk and the Antelope, after the Buffalo shall have utterly disappeared. I do not doubt the assertion of the plainsmen that rain increases as settlements are multiplied. Crossing the Plains in 1859, I noted indications that timber had formerly abounded where none now grows; and I presume that, as young trees are multiplied in the wake of civilization, finally thickening into clumps of timber and beginning a forest, more rain will fall, and the extension of woodlands become comparatively easy. But, relatively to the country eastward of the Missouri, the Plains will always be arid and thirsty, with a pure, bracing atmosphere that will form a chief attraction to thousands suffering from or threatened with pulmonary afflictions. A million of square miles, whereon is found no single swamp or bog, and not one lake that withstands the drouth of Summer, can never have a moist climate, and never fail to realize the need of Irrigation. The Plains will in time give lessons, which even the well-watered and verdurous East may read with profit. Such level and thirsty clays as largely border Lake Champlain, for example, traversed by streams from mountain ranges on either hand, will not always be owned and cultivated by men insensible to the profit of Irrigation. Nor will such rich valleys as those of the Connecticut, the Kennebec, the Susquehanna, be left to suffer year after year from drouth, while the water which should refresh them runs idly and uselessly by. Agriculture repels innovation, and loves the beaten track; but such lessons as New-England has received in the great drouth of 1870 will not always be given and endured in vain. XLVII. UNDEVELOPED SOURCES OF POWER.