'In fact, this assumption of the possibility of obtaining command of an unlimited ascensional force has suggested, to certain enthusiastic partisans of M. Petin's theory and plans, a long perspective of astounding visions, from which sober-minded Englishmen would, in all probability, turn away with derision. These enthusiasts have evidently adopted the language of Archimedes, and are ready to exclaim: "Give us a _fulcrum_, and," with hydrogen gas as our lever, "we will move the world!" 'For ourselves, we have already stated the facts from which we derive our conviction that the conquest of the air, if achieved, is to be brought about through the agency of new and powerful mechanical combinations, rather than by means of the balloon; and though, as before remarked, the experiments of M. Petin and others may probably not be without useful results, we dismiss these brilliant phantasmagoria with the charitable reflection, that the extravagance of overweening hopefulness is, at least in an age which has witnessed the advent of steam and electricity, more natural and more pardonable than the scepticism of confirmed despondency; and that "he who shoots at the stars," though missing his aim, will at all events shoot higher than he who aims at the mud beneath his feet. 'Meantime, the science of meteorology--a subject intimately connected with that of aero-locomotion--though yet in its infancy, already furnishes many indications of great importance, as establishing a very strong presumption in favour of the existence of permanent atmospheric currents, blowing continuously in various directions at different degrees of elevation. 'We know that air, when rarefied by heat, becomes lighter and rises, cold air immediately rushing in to supply its place; and it is evident, therefore, that if two neighbouring regions of the atmosphere are unequally heated, this inequality of temperature will give rise to two currents of air--a warm one, in the upper region of the atmosphere, blowing from the warmer to the colder region; and a cold one, near the surface of the earth, blowing from the colder to the warmer region. It can, therefore, hardly be matter of doubt, that great permanent currents, caused by the unequal heating of the equatorial and polar regions, do exist in the higher strata of the atmosphere--an inference which is supported not only by the occurrence of the trade-winds and the monsoon, but by a variety of other facts and observations. 'Thus, for instance, it is found that in the region of the trade-winds, cinders from the craters of volcanoes, and other objects, are carried through the higher regions of the air in a direction exactly opposite to that in which the trade-wind itself is blowing below; and in this way cinders from the Cosiguina, in Guatemala, frequently fall in the streets of Kingston (Jamaica), lying to the north-east of Guatemala. Similar facts have been observed at the Peak of Teneriffe, in the Straits of Magellan, and elsewhere.