the fact that the early morning may be a specially propitious time for hydropathic transactions; the patients' lungs get the benefit of the cool morning air while his body is revelling in the pond of Siloam, or his feet in the parsonage pasture.
And since cool mornings are rare in the summer season of our lowlands, the "mountain cure" has a legitimate claim to the attention of health-seekers, especially where highlands have preserved their wealth of air-filtering forests. Carbonic acid, the lung-poisoning residium of respiration and combustion, is heavier than the atmospheric air, and accumulates in low places—in wells, in cellars, in deep, narrow valleys, etc.—and often mingles with the malarious exhalations of low, swampy plains. On very high mountains, on the other hand, the air becomes too rarefied to be breathed with impunity. It causes a spasmodic acceleration of the respiratory process, and is, therefore, especially distressing to diseased (wasted) lungs, whose functions are already abnormally quickened, and cannot be further stimulated without overstraining their mechanism.
In the temperate zone the purest and at the same time most respirable air is found at an ele-
