The discordance prevailing between observers, equally honest, equally intelligent, arises, no doubt, from this, that all the elements of the problem to be solved are not yet discovered; nor could this be expected until a refined chemistry had more fully developed the relation between chemical and physiological phenomena. The very essence of the affinities between the soil and vegetable and animal life was a complete mystery until lately, whilst the relations of the superambient atmosphere to the organic remains of what had ceased to live, were wholly misunderstood. The cause of the potato blight, which produced a famine in Ireland, is still a mystery; so also is that of the vine. A disease very fatal to horses, called Paard-sick, from its only attacking the horse, is endemic in some districts of the Cape; that is, in the healthiest country in the world. The nature of the Paard-sick has never been discovered. It spares the _wilde_ of the horse genus--the quagga, zebra, &c.--but is fatal to the domestic breed. Man’s interference, then, proves at times fatal to his protegée. It is everywhere the same, unless his interference be guided by all the lights which the highest reasoning powers, the shrewdest observation, and oft-repeated experience can afford. The two Canadas are in an especial manner the land of rivers, lakes, marshy forests, swampy meadows, and a soil into which the plough never penetrated until the white man appeared. As a natural result, it might be conjectured and presumed that intermittents and remittents, under at least certain of their forms, would be equally frequent and universally diffused. Statistics prove it to be directly the reverse, Upper Canada being to Lower Canada, in respect of these fevers, as 178 intermittents is to 26 remittents; whilst even of these 26 it is affirmed that the greater number of them came from the Upper Province. To show that I do not exaggerate this singular fact, I quote the remarkable statistics of Major Tulloch. “Taking the results of these ten years as the basis of our deductions, then, the prevalence of intermittent fevers in Upper compared with Lower Canada is as 178 to 26. It is necessary, however, to keep in view that all the admissions (amounting only to 26) from intermittent fever in Lower Canada did not originate there, by far the greater proportion of them having occurred among soldiers who came from the Upper Province while labouring under that disease, or who had acquired a predisposition to it during a previous residence there. Indeed, except at Isle aux Naix and the other small stations along the banks of the Richelieu, fevers of the intermittent type are rarely indigenous in Lower Canada; at Quebec they are said to be unknown, and at Montreal nearly so.