In a later volume of the same periodical,[[142]] there is a description of a hill in Virginia where ice is found in summer. This hill lies near the road between Winchester and Romney, on the North River, latitude 39º N. One side of the hill is entirely composed of loose stones from ten to twenty pounds in weight, and under these the ice is found, although their upper surface is exposed to the full sun from 9 or 10 A.M. till sunset. In all seasons there is an abundance of ice. A writer in the 'London and Paris Observer'[[143]] visited the spot on the 4th of July, after a time of stifling heat, and in ten minutes he found more ice than the whole party could have carried away. He did not explore any farther than the foot of the hill; but the neighbours, who used the ice regularly in summer, assured him that it was to be found high up also. A constant and strong current issued from the crevices, stronger and infinitely colder than the current in the famous 'blowing cave' of Virginia. A man had built a store-room for meat within the influence of one of these currents, and hard dry icicles were seen hanging from the wooden supports inside: the flies, too, which had been attracted by the meat, were found frozen on to the stones. This is not the only district where ice is found within temperate latitudes in North America. In Professor Silliman's 'American Journal of Science,'[[144]] in a sketch of the geology of the township of Salisbury, Con. (latitude 43° N.), 'natural ice-houses' are mentioned. These consist of chasms of considerable extent in the mica-state, where ice and snow remain during the greater part of the year. The principal of these chasms lies in the east part of the town, and is several hundred feet long, sixty feet deep, and about forty wide. The slate is of a very compact kind; and the walls are perpendicular, and correspond with much exactness. At the bottom is a cold spring, and a cave of considerable extent, in which it is probable that the ice lies--for the writer does not specify the position in which it is found. The chasm is a favourite retreat in summer, and is called the Wolf-hollow, from its having formerly been a famous haunt for wolves.
Similar receptacles for summer-ice are found in several places in North America. In the forty-ninth volume of the Sitzungsberichte der Kaiserl. Akademie in Wien (1te. Abth.), a list of references to various ice-holes is appended to a paper by Dr. Boué on the geology of Servia. Many of the passages referred to have nothing to do with ice-caves, as, for instance, the sections of De Saussure's book describing his observations of 'cold caves', or the account of the mass of ice and snow from which the river Jumna springs, for which Dr. Boué refers to the 'Philosophical Magazine' for November 1823, meaning, in fact, the 'London Magazine'. The 'Description des Glacières' of M. Bourrit is also given as a part of the literature on ice-caves; whereas (see the account of the Glacière of Montarquis, in the Valley of Reposoir) by 'glacière' M. Bourrit meant only a locality where ice is to be found, or a glacier district. Dr. Boué, however, gives some references to the 'American Journal of Science' which it is possible to make out by a careful search in the neighbourhood of the volume and page he mentions. In vol. iv. (1822,--Dr. Boué says 1821) there is an account by the editor[[145]] of a natural ice-house in the township of Meriden, Con., between Hartford and Newhaven, at an elevation of not more than 200 feet above the level of the sea. The ice is found in a narrow defile, which is hemmed in by perpendicular sides of trap-rock, and displays a perfect chaos of fallen blocks of stone. The defile is so narrow, that the sun's rays only reach it for an hour in the course of the day; and even the trees and rocks, and beds of leaves, protect the ice from any very material damage. Dr. Silliman visited this defile on the 23rd July, 1821,[[146]] with Dr. Isaac Hough, the keeper of a neighbouring inn, and found that the ice was only partially visible, in consequence of the large collection of leaves which lay on it: they sent a boy down with a hatchet, and he brought up some large firm masses, one of which, weighing several pounds, they carried twenty miles to Newhaven, where it did not entirely disappear till the morning of the third day. Seven miles from Newhaven, in the township of Branford, there is a similar collection of ice. In both of these cases, the ice is mixed with a considerable quantity of leaves and dirt.
In the same volume (p. 331,--Dr. Boué says p. 33), two accounts are given of a natural ice-house near the summit of a hill in the neighbourhood of Williamstown (Mass.). In the next volume there is a further account of it by Professor Dewey, stating that since the trees in the neighbourhood had been cut, the snow and ice had disappeared each year about the first of August.
In vol. xlvi. (p. 331) an ice mountain in Wallingford, Rutland County (Vt.), is described, which is ordinarily known in the neighbourhood as the ice-bed. An area of thirty or fifty acres of ground is covered with massive débris of grey quartz from the mountains which overhang it; and here--especially in a deep ravine into which many of the falling blocks of stone have penetrated--ice is found in large quantities. It appears to be formed during the melting of the snow in February, March, and April, and vanishes in the course of the summer, in hot years as early as the last days of June.
These descriptions call to mind the Glacière of Arc-sous-Cicon, in which many of the features of the American ice-caves are reproduced. An American photograph is current in this country, in the form of a stereoscopic slide, representing an ice-cave in the White Mountains, New Hampshire; but it is only a winter cave, and in no way resembles any of the glacières I have seen. It is merely a collection of long and slender icicles, with beds of ice formed upon stones and trunks of trees on the ground; nothing more, in fact, than is to be seen in any tolerably severe winter in the neighbourhood of a cascade in a sheltered Scotch burn.
The 'American Journal of Science' (xxxvi. 184) gives a curious instance of a freezing-well near the village of Owego, three-quarters of a mile from the Susquehanna river. The depth of the well is 77 feet, and for four or five months in the year the surface of the water is frozen so hard as to render the well useless. Large masses of ice have been found in it late in July. A thermometer, which stood at 68° in the sun, fell to 30° in fifteen minutes at the bottom of the well; and the men who made the well were forced to put on thick clothing in June, and even so could not work for more than two hours at a time. No other well in that neighbourhood presents the same phenomenon. A lighted candle was let down, and the flame became agitated and thrown in one direction at a depth of 30 feet, but was quite still at the bottom; where, however, it soon died out. The water is hard or limestone water.
Rocks of volcanic formation would seem to afford favourable opportunities for the formation of ice. Scrope mentions this fact in an account of the curious district called Eiffel or Eifel, in Rhenish Prussia, which was published originally in the 'Edinburgh Journal of Science,'[[147]] and has since been translated in Keferstein's Deutschland.[[148]] The village of Roth, near Andernach, is built on a current of basalt, derived from the cone above it, which has at some time sent down a stream of lava to the north and west. A small cavern near the village, forming the mouth of a deep fissure in the lava-stream, half-way up the cone, displays a phenomenon which the writer says he has often observed in volcanic formations. The floor of the cavern was covered with a crust of ice at the time of his visit, about noon on a very hot day in August. The peasants report that there is always ice in summer, and never in winter, when the sheep retreat to the cave on account of its warmth. Steininger[[149]] found a thickness of 3 feet of ice on September 19, 1818, but it was evidently in a melting state, and the thermometer stood at 36·5 F. in the cavern. He describes it as possessing a narrow entrance facing north, entirely sheltered from the sun by lava-rocks, and by the trees of a wood which covers the cone of scoria.
Scrope believes that this is the mouth of one of the arched galleries so frequently met with under lava in Iceland, Bourbon, and elsewhere; and on this he founds his explanation of the phenomenon. If the other extremity is connected with the external air at a much lower level, a current of air must be constantly driven up this gallery, and in its passage will be dried by the absorbent nature of the rock--which is perhaps partly owing to the sulphuric or muriatic acid it contains[[150]]--- and the evaporation caused by this current produces a coating of ice on the floor of the grotto, where there is a superficial rill of water. The more rarified the lower external air, the more rapid will be the current of cool air; and, therefore, the greater the evaporation. The winter phenomenon is to be explained by the fact that the current of air will be about the mean annual temperature of the district, taking its temperature, in fact, from the rocks through which it passes; and, therefore, by contrast the grotto will appear warm.
The same writer mentions a similar example of summer ice in Auvergne.[[151]] There is a natural grotto in the basalt near Pont Gibaud, some miles to the north-west of Clermont, in which a small spring is found partly frozen during the greatest heats of summer, while the water is said to be warm in winter; probably, Scrope observes, only seeming to be warm by contrast with the external temperature. The water is apparently frozen by means of the powerful evaporation produced by a current of very dry air proceeding from some long fissures or arched galleries which communicate with the cave. In this case also the writer suggests that the air owes its dryness to the absorbent qualities of the lava through which it passes: he repeats, too, the remark that the phenomenon is of common occurrence in caverns in volcanic districts.[[152]]
There is a remarkable instance of ice occurring under lava, near the Casa Inglese on Mount Etna, which it may be as well to mention, though the causes of its existence have probably nothing in common with the phenomena of ice-caves, or summer ice. An account of it is to be found in Sir Charles Lyell's 'Elements of Geology.'[[153]] It appears that the summer and autumn of 1828 were so hot, that the artificial ice-houses of Catania and the adjoining parts of Sicily failed. Signer M. Gemmellaro had long believed that a small mass of perennial ice at the foot of the highest cone of Etna was only a part of a large and continuous glacier covered by a lava current, and from this he expected to derive an abundant supply of ice. He procured a large body of workmen, and quarried into the ice; but though he thus proved the superposition of lava for several hundred yards, the ice was so hard, and the expense of quarrying consequently so great, that the works were abandoned. This was on the south-east of the cone, not far from the Casa Inglese. Sir Charles Lyell suggests that, probably, at the commencement of some eruption, a large mass of snow has been thickly covered with volcanic sand, showered upon it before the arrival of the lava itself. This sand is a non-conductor of heat, and would therefore tend to preserve the snow from complete fusion when the hot lava-stream passed over it, and thus the existence of the underground glacier may be explained. The peasants of the district are so well acquainted with the non-conducting properties of volcanic sand, that they secure an annual store of snow, for providing water in summer, by strewing a layer of sand a few inches thick upon a field of snow, thus effectually shutting out the heat of the sun. It is curious that when De Saussure visited Chamouni for the first time, his attention was arrested by the sight of women sowing what seemed to be grain of some kind in the snow; but, on enquiring, he found that it was only black earth, which the inhabitants spread on the snow in spring, in order to make it disappear sooner. He was told that snow thus treated would melt a fortnight or three weeks before the ordinary time for its disappearance in the valley; but it will be seen that this does not contradict the theory of the Sicilian peasants.[[154]]