Let me now consider briefly--keeping the same object in view, namely, its influence on man--what are the sources and results of that amount of hydrogen or azote which plays so important a part in the economy of all that lives. An agricultural farmer at a distance from markets sufficiently remunerative, has a large field of turnips which he knows not how to dispose of. Not having cattle or sheep sufficient to consume these turnips, he addresses himself to drivers of sheep on the way to the markets, inviting them to turn their sheep into the field, and there remain until the turnips are consumed. Thus he hopes to restore to the field the azotized and other principles removed from it by previous crops, and to prepare the way for fresh and more productive and profitable crops. It is on the same principle that in many leases of farms (those called steel-bow) there is an express clause that the straw shall not quit the farm, but be consumed on it. The object of this is simply to restore to the soil what forced crops have removed from it. Man has taken on himself the task of growing on one acre the natural produce of many; to feed twenty men instead of one from off the same extent of soil; to live in crowded cities, drawing their provisions from the surrounding country, producing nothing of themselves; to feed millions where nature intended but a few thousands should exist; he has taken the task on himself and must carry it through, exposed to destruction at every false step, and at this moment exposed to the accusation by the medical authorities of England of deliberately rendering his farm-house, his homestead, his cottage, his mansion, his palace, a pesthouse, the propagator, if not the absolute generator, of all the wide-spread plagues and pestilences, from that which desolated Athens in the time of Thucydides; laid waste the Roman world when Justinian reigned; smote England in the most unhappy and disgraceful period of past history;[42] and now, appearing amidst the tents of an obscure Arab tribe, ignorant of agriculture, living with their flocks and herds on the desert, happily remote from the influences of boards of health, officers of health, and registrars-general, once more threatens Europe; he is accused, in fact, of being the involuntary but certain slaughterer of his little babes. So says the eloquent Registrar-General of England in one of his sanitary reports; he belongs, it is true, and this must not be forgotten, to the theory-loving fraternity,[43] a professor, in fact, of that conjectural art which heretofore despised statistics, and which now, by mistaking figures for facts, threatens to convert true science into a scheme of fictions anything but brilliant. To the Chadwicks, the Gavins, and a host of others still more potent, but who always act through the agency of _employées_, we owe the affair of Luton and of Birmingham, of the disgraceful condition of the Thames and