And each new plant brings with it new conditions of life, new wants, new virtues, new uses, new whims, if we may so speak, to be humoured. The iron, and the timber, and the brass are always one and the same to the mechanist; but with the constitution of each new plant, and its habits, a new series of difficulties opens up to the cultivator, which only time and experience, and much study, can overcome. But mechanics also exert much influence upon the culture of the soil, and the rearing of useful plants. And though the greatest achievements of mechanical skill were not first made on her behalf, yet even the steam-engine may be said to have become auxiliary to agriculture; and the thousand ingenious implements which Northampton and York exhibited at their recent anniversaries, showed in how many quarters, and to how large an extent, the purely mechanical and constructive arts are expending their strength in promoting her cause. On meteorology, which studies the aërial meteors--registers, tabulates, and gives even a local habitation and a form to winds, hurricanes, and typhoons--the progress of the navigator much depends. They hinder or hasten his progress; but he overcomes them at last. But atmospheric changes are vital things to the plant and to the soil. Where no rain falls, the plant withers and dies. If too much falls, it becomes sickly, and fails to yield a profitable crop. If it falls too frequently, though not in too large quantity on the whole, one plant luxuriates and rejoices in the genial season, while another with difficulty produces a half return. If it falls at unseasonable times, the seed is denied admission into the ground in spring, or the harvest refuses to ripen in the autumn. So the warmth and the sunshine, and the evening dews and the fogs, and the electric condition of the air--its transparency and its varying weight--and prevailing winds and hoar-frosts, and blights and hail-storms, and the influence of the heavenly bodies on all these conditions--with all these things the interests of the plant and the soil demand that scientific agriculture should occupy herself. On every single branch of knowledge to which we have alluded, the power and skill profitably to influence the plant are dependent.