Alabama state intelligencer., 1831-06-18
From the Charleston Courier.
Theory ef Haa from silliman's Jonrmal

From the Charleston Courier. Theory cf Hail from Salinam's Journal l We make below an abstract of portion Iot very ingenious and philosophical paper on this subject, by Professor OLMsrEAD.- lOur readers will no doubt perceive the coin lcidence between the late cool weather and the hal storms, of which we have lately had re- lpeated accounts.
 The theories heretofore received on this sub Vect, have been very unsatisfactory, and per lhaps we are not venturing too much to say, that the one now extracted from &liiman'S IJournal will be found true enough to account tor all the phenomena which the old specula- ltions left unexplained
 | We recommend those who are curious in these inquiries, to vol. XVIII. No. l of the Journal, where they will find the matter treat led at greater length than our limits would permit us to copy.
 l. Hail Storms, when violent, are charac- ltersed by the meeting of all the clements of storms; the clouds are very black; they are strongly agitated, and fly swiftly through the air, or more frequently rush towards each other, attended by high winds and terrific thunder and lightning.
 2. Hail storms, of the foregoing character, arc confined chiefly to the temperate zones
 hey rarely occur in any form in the torlid zone; and when they do, it is chiefly on high mountains.
 3. The most violent hail storms occur chief ly during the warm half of the year, and most frequently in tho hottest months
 4. he hail stones that fall during the same storm, are found to be much smaller on the tops ot mountains than in the neighboring plains.
 5. Though hail stones are of various forms. vet frpOnept1ty tl,o nucleus which is white and porous, while the other parts consist of concentric layers of ice, either transparent of an opaque white, or all ternately transparent and opaque. 6. A shower of hail during the warm sea- son of the year, is often followed by cooler weather; in spring and fall particularly, hail
 IS a well known precursor of cold.
 
 It is well known fact, that the atmosphere grows continually colder as we recede from the earth, until at certain elevation we reach the temperature of freezing water, called the term of congeiation; that the height of the term of congelation above the surface of the earth varies with the latitude, being greatest at the equator, but coming very near to the earth at the pole; that its average height at the equator is about fifteen thousand feet, at the lat. of 30 deg. twelve thousand feet, and at the lat. of 50 deg. six thousand; that be- yond this line of perpetual congelation the reduction of temperature still proceeds until
 it shortly reaches degree of cold the most
 intense that can be imagined. If we now con- template a current of air, that is, wind blowing horizontally first at the surface of the earth and afterwards at different elevations, we shall find that it will be subject to the fol- lowing notifications. We will suppose it to blow first from the polar towards the equa- torial regions When it moves at the surface of the earth it will rapidly imbibe the heat of the earth as it traverses the warmer attitudes; at the height of one thousand feet it will feel the influence ofthe earth much less, and grow warm much slower than before; and at the height of ten thousand feet, it will, for the most part, sweep quite clear of the noun tains, and be current of air blowing through the atmosphere alone. And since, as in the case of the Gulf Stream, fluid does not req dily change it's temperature merely by flow ing through body of the same fluid of diff fereEt temperature, and especially air by flowing through air, a wind blowing from north to south, at an elevation of ten thousand feet above the earth, will pass to great dis tance without materially altering its tempe rature. What we have here supposed respect ing the heating of northerly wind as it blows southerly, will obviously apply to the cooling of southerly wind as it blows northerly; and since high wind frequently moves at the rate of sixty miles or about one degree an hour, especially where it passes without obstruc- tion in the upper regions of the atmosphere, it would consequently pass over ten degrees in the short space of ten hours.
 These things being clearly understood, we assign as the cause of hail storms, the congo iation of The 7vatery vahor of q body ofzoarm and humM air, by its suddenly miring zuih on exceedingly cold zvind, in Me higler re- gions ofthe atmoshhcre. Let us examine the effects which would result from the meeting of two opposite winds, at the height ot ten thousand feet, during the heat of summer, the one blowing from the latitude ot 30 deg. or from the confines of the torrid zone, and the other from the latitude of 50 deg. or the northern part of British America. If they had equal lvelocites, they would meet at the parallel of 40 deg. that is, at our own latitude, in ten hours from the time of setting out; and according to what has been promised, each current would retain nearly the original tenn perature. The southerly wind blowing from a point which is still two thousand feet below the line of perpetual congelation, is compara- lively warm, while the northerly wind con- ing from point which is four thousand feet above the same boundary of the empire of frost, will have degree of cold probably sur passing any with which we are acquainted. We infer from our preliminary principles, that immediately on meeting, the watery va DOT of the warmer current would be frozen with an intensity corresponding to the tempe rature of the colder current; that the minute hail stones thus formed, and endued with such excessive cold, would begin to descend, and accumulate to size proportioned to the intensity of the cold of the original nucleus to the space through which they descended and to the humidity of the lower strata ofthe ntr kat th,,c tl,e colder. the heN