Page:Works of the Late Doctor Benjamin Franklin (1793).djvu/195

185 turn often without finding repoſe in any poſition. This fidgettineſs, to uſe a vulgar expreſſion for want of a better, is occaſioned wholly by an uneaſineſs in the ſkin, owing to the retenſion of the perſpirable matter—the bed-clothes having received their quantity, and, being ſaturated, refuſing to take any more. To become ſenſible of this by an experiment, let a perſon keep his poſition is. the bed, but throw off the bed-clothes, and ſuffer freſh air to approach the part uncovered of his body; he will then feel that part ſuddenly refreſhed; for the air will immediately relieve the ſkin, by receiving, licking up, and carrying off, the load of perſpirable matter that incommoded it. For every portion of cool air that approaches the warm ſkin, in receiving its part of that vapour, receives therewith a degree of heat, that rarifies and renders it higher, when it will be puſhed away, with its burthen, by cooler, and therefore heavier freſh air; which, for a moment, ſupplies its place, and then, being likewiſe changed, and warmed, gives way to a ſucceeding quantity. This is the order of nature, to prevent animals being infected by their own perſpiration. He will now be ſenſible of the difference between the part expoſed to the air, and that which, remaining funk in the bed, denies the air acceſs: for this part now manifeſts its uneaſineſs more diſtinctly by the compariſon, and the ſeat of the uneaſineſs is more plainly perceived, than when the whole ſurface of the body was affected by it.

Here, then, is one great and general cauſe of unpleaſing dreams. For when the body is uneaſy, the mind will be diſturbed by it, and diſagreeable ideas of various kinds will, in ſleep, be the natural conſequences. The remedies, preventative, and curative, follow: