Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

sign in the evening, but an unfavorable sign if in the morning. The form and appearance of the clouds themselves are full of significance. If their forms are generally soft, undefined, and feathery, then will the weather be fine. If their edges appear hard, sharp, and well defined, it will be foul. Besides, gener- ally speaking, any unusual hues, as the deep, dark, or very gay, betoken wind, or some falling weather, (rain, snow, hail, &c.;) while the more moderate and delicate tints bespeak fair weather. Lightning: M. Arago says there arc three kinds of lightnings —the forked, the sheet, and the spherical. The forked lightnings are in slen- der white or bluish streaks, that are zigzag or crinkled, and sometimes divided or forked. This is the most common kind. The sheet lightning, he says, is uniformly of a dull red appear- ance. The spherical are the same as thunderbolts, which de- scend more seldom and slowly to the earth, according to a law of their own, rendering lightning rods, as for them, useless. But there are also recognized two kinds of electricity in the atmosphere, so that the one or the other is always prevailing and affecting the health of mankind according to the weather; or, rather, according to the prevalence of this or that kind of electricity, so is the weather. The one is vitreous or positive, the other is called resinous or negative. These two forms of electricity are produced in the atmosphere itself from various causes — chiefly from evaporation, more also from conden- sation and separation of its moisture; from vegetation, from combustion, and from friction. This latter arises from large masses of air, moving in contrary directions, and thus encoun- tering or chafing one another. The friction on the edges of such currents develops free electricity, which is more especially active when these moving masses of air, arising from different quarters and at different altitudes, differ also in their respective degrees of moisture and temperature. The cold develops neg- ative electricity, the warm the positive electricity. Thunder storms, then, are the result of the approximation of vast quan-