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

2. When the rain has approached within a certain distance, we find a strong negative electricity; and this not unfrequently produces sparks to the fixed conductor. 3. When the rain has reached the place of observation, a great quantity of positive electricity has rapidly come, as found again indicated. 4. When the rain has passed over and gone, we now have again a strong negative tension ; but this for a very short time. 5. Finally, when the rain is sufficiently distant, so that the zone also has passed off with it, the atmosphere returns to its habitual equilibrium or mean ; i. e., for the time of clear weather; of moderately positive electric tension. Therefore we can rec- ognize in this a law of three marked electric changes. First, that at the approach of the storm, which is negative. Second, that which prevails during the storm and fall of the rain or snow, which is positive. Third, that which follows close on its departure, which is again negative; but that this latter is not so marked, or of so long duration ; and this is again succeeded, as we have said, by that clear, serene sky that we call a pure atmos- phere, possessing its full quantum of natural electricity, and no more. It is believed that negative or neutral rains do not come ; that negative clouds do not exist. When the air is perfectly pure, the upper stratum of it is electrized positively in respect to the lower strata, while at the same time the surface of the earth is nearly neutral, and hence the electricity of the atmos- phere must increase as we rise. To test or prove this, M. Bec- querel ingeniously employed arrows shot from a cross-bow. To the arrow, when shot, was attached a fine silk thread neatly cov- ered with tinsel, the other end of which communicated with an electroscope. He thus fairly and beautifully demonstrated the increased ratio of positive electricity in the atmosphere to be in direct proportion to the height in the air. He made this experiment at the Great St. Bernard, in Switzerland, and upon the top of one of those elevated plateaus near the Hospice. But our space allows us merely to allude to all these highly interesting and instructive observations, made by the aid of the telling Electrometer for testing atmospheric electricity, as to