Licence: Public Domain Mark
Credit: The atmosphere in relation to human life and health. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![particles are attracted with ever-increasing strength. In this way, in addition to mere impact, in the course of a fall of 10,000 or 15,000 feet,' are formed those large liailstones which devastate crops and kill animals- Taking Aitken's observations of tlie number of i)articl(!S of water or droplets of fog, falling upon a square inch in a minute in a dense fog, as a criterion—say, namely, an average of about 10,000 droplets—and assuming that these drops fall at the rate of not more (it is probably much less) than 10 feet a minute, a hailstone falling through 10,000 feet of dense cloud would encounter if it began as a snowflake, 1 inch s<]uare, about 10,000,000 droplets, by mere imjiact. Some hailstones may result from the attraction of small spicules of ice and particles of water alternately as the nucleus i)asses through different strata, and these show concentric bands alternately opaque and clear. Similar bands may be formed by the passage of the hailstone througli alternate spaces of thick cloud and of clear, unclouded, but saturated air. The latent heat brought into the sensible condition by condensation and congelation has been supposed to make such an accumulation in clear, saturated air impossible, but actual observation indicates that the rai>id passage of the hailstone through very cold air speedily and continuously dissipates the heat thus set free. The appearance of spaces between successive tiers of dense cumulus cloud and the almost invariably excessive display of electric phenomena are characteristic of great hailstorms. It is very probable that between the dense clouds lie masses of saturated, or even sui)ersaturated, almost dust-free air. A cold hailstone falling through these would accumulate ice in clear, alternate zones surrounding the nucleus. Large hailstones are gen- erally spheroidal, small ones conical, with icy bases and a softer apex. The large hailstones are probably more dependent on electric attrac- tion, and the small on the impact of descent, for their form and icy accumulations. In a thunderstorm or shower, the lower clouds are generally nega- tively and the upi)er positively electrified. Before a hailstorm clouds of great significance may be observed, which may be described as tur- reted cumulus or cumulo-stratus. They are quite distinctive of hail- storm weather, though of course the hailstorm may not occur in the district where they are seen. They consist of hard-looking, sharply defined, generally white, and rather small masses of cloud, with pro- jections towering upward and rather broader at the top than at the base, or equally broad. These peculiar clouds are worthy of note with the view of forecasting the probable occurrence of hailstorms. Vapor, when it ceases to exist as a gas in the air, assumes several 'The height of cumulus cloud may often be well observed and measured not only from the plain, but on mountains. The tower of cumulus cloud often exceeds 10,000 or 15,000 feet, and in great storms may be 25.000 to 40.000 feet from base to summit. Both observations from the earth and balloon ascents supply evidence to this effect.](https://iiif.wellcomecollection.org/image/b21208724_0037.jp2/full/800%2C/0/default.jpg)
