In the lower parts of the country, near the large rivers, the lands are flat and the declivity towards the sea-coast much more gradual than here. Hence, the water there descends with less rapidity, and is not so pure; hence, too, there are many more stagnant collections of it, which may be considered as so many seminaries of disease. On the rivers, too, are extensive tracts of marshy land, many parts of which are so miry that, without exaggerating, you may with a light impulse of the hand, bury a ten-foot rod in a perpendicular direction. These are covered with a luxuriant growth of grass and weeds in summer, and with a thick coat of dry sedge in winter; so that, except in the spring, when these places are set on fire, they are utterly impenetrable to sun or air, excluding the salubrious blasts of the one and the purifying rays of the other, and remain ever fraught with noxious and morbific particles. Hence arise fogs, prodigiously dense, impregnated with unwholesome vapors, arising from these sloughs, and extremely offensive to the smell, which often continue undispersed till nine o'clock in the morning, by which probably the purity and salubrity of the air is impaired. From the evils of these treasuries of disease we mountaineers are happily exempt. The descent of our lands is so quick, that morasses are scarcely known among us, and the rapidity of our waters so great that none of them have leisure to stagnate. Now, the difference between the air of London and that of the country may possibly be as great as between that of a lowland and mountainous situation here; for, methinks it is highly probable, that the smoke and filth of that prodigious city may infect and pollute the air as much as the exhalations from our marshy grounds. Whether these speculations be just or not, I, who never made philosophy my study, will not undertake to decide, but it is
