The Massachusetts Spy, And Worcester County Advertiser

Aerial Barrier. The extreme rarity of the air on high mountains must, of course, affect animals. A person breathing on the summit of Mont Blanc, although expanding his chest as much as usual, really takes in at each inspiration only half as much air as he does below, exhibiting a contrast to a man in a diving-bell, who, at thirty-four feet under water, is breathing air of double density; at sixty-eight feet, of triple, and so on. It is known that travellers, and even their practised guides, often fall down suddenly, as if struck by lightning, when approaching lofty summits, on account chiefly of the thinness of the air which they are breathing, and some minutes elapse before they recover. It appears from all this, that although our atmosphere be fifty miles high, it is so thin beyond three miles and a half, that mountain ridges of greater elevation are nearly as effectual barriers between nations of men, as are islands or rocky ridges in the sea, between the finny tribes inhabiting the opposite coasts.