cate or the subject of that proposition, by means of the same faculty, suggests a second proposition having a common link with the first, whereupon the mind intuitively sees the conclusion. Suppose, for example, that the idea of commerce being presented to the mind, the associating or repeating faculty suggests that of wealth, as one of its proximate effects. Then, either wealth or commerce, by the ever ready agency of the same repeating faculty, may suggest a second proposition. In the first case, the reasoning, reduced to syllogistic form, would be as follows: Commerce is productive of national wealth. In the second case, by a like process, the reasoning would be in this mode: Commerce is productive of national wealth. Commerce has flourished most in free States. Therefore, civil freedom is not inconsistent with national wealth. And so through all the moods and figures of which human reason is capable. In conclusion, I would remark, that according to the simple view of the associating faculty here taken, there seems to be no difference between the mental operations of memory and recollection, except that in the last we watch the operations of our mind in order that when, in its ceaseless repetitions, it may chance to light upon the fugitive thought we are in pursuit of, we may profit by it. But in both cases the mind copies its former states, and obeys the same laws. It, therefore, is not to be believed that if Aristotle had distinctly seen that there were the same principles of connexion in both, or that the mind, in no train of thought whatever, could pass from idea to idea, except by one of the connecting links he had mentioned when treating of recollection, he would not have expressly stated it; nor, if he had seen, as Brown did, that memory and imagination were merely modes of the same faculty of association, that he would have treated of them in different parts of his work, without the slightest notice of their kindred character; and, lastly, were we to concede to his brief and somewhat obscure views on this branch of psychology, that very liberal and favourable interpretation which Sir William Hamilton has given, it is still quite clear that he did not perceive that all the mental operations and phenomena of which he separately treats could be resolved into the mind's repetition of its own operations. It is as unnecessary to his glory, as it is unjust to others, to deny all merit to succeeding inquirers. MIST AND CLOUDS. ▾ (In Vol. II. of the Register, page 477, will be found a brief article under this title, explaining the phenomena of mist and clouds. We now copy from the National Intelligencer, the following communication of the learned Dr. Robert Hare, in opposition to the theory there stated-a duty we owe to the cause of science.) Strictures on an article entitled Mist and Clouds, in the American Register for June last. By ROBERT HARE, M. D., Emeritus Professor of Chemistry in the University of Pennsylvania, and Associate of the Smithsonian Institution. I have had much pleasure and have received much valuable information in reading "Stryker's American Register" for June. I object to the article on Mist and Clouds as tending to convey erroneous ideas. In that article it is stated that, agreeably to Sir Humphrey Davy, mists and clouds are produced by the "radiation of vapour;" and, moreover, it is alleged that mist, when "negatively electrified," deposites vapour more quickly, forming a heavy sort of dew. The idea that vapour, when negatively electrified, deposites dew more copiously can only be true when the bodies which it moistens are differently electrified. I cannot understand why the deposition should be greater when the dew is negative and the bodies positive than when these are negative and the dew positive. In either case, the attraction is reciprocal, and the action and reaction equivalent. Not less new to me is the suggestion that vapour can be “transferred by radiation," though it be well known that it may give out heat by radiation, so as to be refrigerated and condensed. Agreeably to the received Daltonian theory, water being present in excess, the amount of vapour in any given space will be directly as the temperature, whether air be present or not; in other words, it will be no less plentiful in a receiver replete with air than in one exhausted by an excellent air pump. A mist or fog invariably results when air saturated with moisture at any temperature is refrigerated. Of course it ensues whenever air and water, at different temperatures, are brought into contact. The vapour due to the temperature of the water, when this is the warmer of the two, in rising into strata of the air too remote from the water to be sufficiently warmed by it, must be condensed by refrigeration. When the air is the warmer, the vapour with which it may be saturated, giving out its heat to the water by radiation or circulation, is of course converted into a mist or fog. Thus a wind blowing over the Gulf Stream is consequently warmed and supplied with an excess of vapour, which condenses on reaching the cooler aquatic region between the banks of Newfoundland and the neighbouring coast of North America. The moisture which, in the state of vapour during autumnal days, rises into the atmosphere, being condensed during the succeeding chilly nights, subsides as a fog, which is more or less dense and extensively prevalent in proportion to the difference between the temperature of the day and night. Clouds are caused by rarefaction as well as cold. This explains their being formed when air, saturated by moisture, reaches a certain elevation, where the atmospheric temperature and pressure and density are diminished. Moreover, at the moment of rarefaction, air robs the moisture of its heat and precipitates it as a fog. This was adverted to by Davy, in his elements, as the cause of clouds. It is just at the point where cold and rarefaction concur to condense the contained vapour that clouds are seen usually flitting above us. It is well known that the surface of a vessel of cold water, exposed in a warmer atmosphere, becomes covered by a dew. The greater the quantity of aqueous vapour mingled with the air, the less the refrigeration requisite to produce this deposition. The highest temperature at which this dew can be obtained is called the dew point; and in proportion as this dew point, determined by a thermometer, is higher, the vapour is more abundant. Obviously, precisely the same reduction of heat which induces dew on a refrigerated surface would produce a fog or cloud, were it to take place in an adequate mass of air containing aqueous vapour. Whenever a given weight of air is augmented in bulk, it must of course occupy a proportionally greater space, and will, in consequence, receive a quantity of aqueous vapour commensurate with the additional space. Consistently, an opposite change in its dimensions will have the opposite effect; so that, if saturated with vapour, a portion of this must be condensed commensurate with the space of which it may be deprived. If, while the bulk of air remains unchanged, another portion of air, equally moist, be superadded to it, so as to increase proportionally the density of the resulting aggregate, all the vapour associated with the additional air will precipitate as fog or as rain. As is it universally admitted that similarly electrified particles recede from each other proportionably to the intensity of the charge by which they may be affected, it seems inevitable that a charge of electricity must occasionally augment the bulk of extensive portions of the atmosphere, and thus cause more vapour to be associated with them; and that when discharges take place of electricity, so as to neutralize the excitement, the moisture held, in consequence of the excitement, must be precipitated. Thus, the air under the influence of electricity may be compared to a sponge under that of the hand, by which it may be made, by alternate pressure and relaxation, to receive and give out the water with which it may be contiguous. I am under the impression that this agency of electricity is not sufficiently recognised by the meteorologists, if it has not entirely escaped them. WINTER QUARTERS IN THE ARCTIC CIRCLE. The approach of winter in the Arctic Circle is attended with many interesting changes. Snow begins to fall as early as August, and the whole ground is covered to the depth of two or three feet before the month of October. Along the shores and bays the fresh water, poured from the rivulets, or drained from the thawing of former collections of snow, becomes quickly converted into solid ice. As the cold augments, the air deposites its moisture in the form of a fog, which freezes into a fine gossamer netting, or spicular icicles, dispersed through the atmosphere, and extremely minute, that might seem to pierce and excoriate the skin. The hoar frost settles profusely, in fantastic clusters, on every prominence. The whole surface of the sea steams like a lime-kiln, an appearance called frost-smoke--caused as in other instances of the production of vapour, by the water being still relatively warmer than the incumbent air. At length, the dispersion of the mist, and consequent clearness of the atmosphere, announce that the upper stratum of the sea itself has cooled to the same standard; a sheet of ice spreads quickly over the smooth expanse, and often gains the thickness of an inch in a single night. The darkness of a prolonged winter now broods impenetrably over the frozen continent, unless the moon chances at times to obtrude the faint rays, which only discover the horrors and wide desolation of the scene. The wretched settlers, covered with a load of bear skins, remain crowded and immured in their hut, every chink of which they carefully stop against the piercing cold; and, cowering about the stove or the lamp, they seek to doze away the tedious night. Their slender stock of provisions, though kept in the same apartment, is often frozen so hard as to require to be cut by a hatchet. The whole of the inside of their hut becomes lined with a thick crust of ice; and if they happen for an instant to open a window the moisture of the confined air is immediately precipitated in the form of a shower of snow. As the frost continues to penetrate deeper, the rocks are heard at a distance to split with a loud explosion. The sleep of death seems to wrap the scene in utter oblivious ruin. Sir Edward Parry has thus beautifully described this effect: "The sound of voices, which, during the cold weather, could be heard at a much greater distance than usual, served now and then to break the silence which reigned around us; a silence far different from that peaceable composure which characterizes the landscape of a cultivated country; it was the death-like stillness of the most dreary desolation, and the total absence of animated existence." During the winter at Melville Island people were heard conversing at the distance of a mile. This was no doubt, owing to the density of the frigid atmosphere, but chiefly to the absence of all obstruction in a scene of universal calm or darkness. Here Melville Island was discovered on September 4th, 1819. Parry and his companions pushed forward, but soon found their course arrested by an impenetrable barrier of ice. They waited a fortnight, in hopes of overcoming it; and, about the 20th, their situation became truly alarming. The young ice began rapidly to form on the surface of the waters, retarded only by winds and swells; so that the commanding officer was convinced that, in the event of a single hour's calm, he would be frozen up in the midst of the sea. No option was, therefore, left but to return, and to choose between two apparently good harbours, which had been recently passed on Melville Island. Not without difficulty he reached this place on the 24th, and decided in favour of the more western haven, as affording the fullest security: but it was necessary to cut his way two miles through a large floe (a small expanse of salt-water ice) with which it was incumbered. To effect this arduous operation the seamen marked with boarding-pikes two parallel lines, at the distance of somewhat more than the breadth of the larger ship. They sawed, in the first place, along the path tracked out, and then by cross-sawing, detached large pieces, which were separated diagonally, in order to be floated out; and sometimes boat sails were fastened to them, to take advantage of a favourable breeze. On the 26th, the ships were established in five fathoms water, at about a cable's length from the beach. For some time the ice was daily cleared round them. But this was soon found to be an endless labour, and they were allowed to be regularly frozen in for the winter. The usual winter protection for the vessels is covering in the deck. Sometimes a house is erected on the shore, with blocks of ice, which soon become a solid concrete mass, which, being a slow conductor, checks the access of cold. It was necessary to be very economical of fuel, the small moss and turf which could be collected being too wet to be of any use. By placing the apparatus for baking in a central position, and by several other arrangements, the cabin was maintained in a very comfortable temperature; but still, around its extremities and the bed places, steam, vapour, and even the breath, settled first as moisture and then as ice. To remove these annoyances became, accordingly, a part of their daily employment. To keep the men's minds in a lively and cheerful state, plays were performed, Lieutenant Beechy being nominated stage-manager, and the other gentlemen coming forward as amateur performers; the Arctic management and the North Georgian Theatre were very popular. The officers had another source of amusement in the North Georgian Gazette, of which Captain Sabine became editor, and all were invited to contribute to this chronicle of the frozen regions. Even those who hesitated to appear as writers, enlivened the circle by good-humoured criticisms: |