based upon that peculiar quality of ice which was brought to light by Mr. Thompson, and which we have already explained in these pages. To make the conception clearer, let us suppose gradually increasing pressure, applied to a mass of ice filled with airbubbles. The ice, as we know, is not of quite uniform composition; it contains some impurities, and the air-bubbles are not quite evenly distributed, nor are they similar in size and shape. At some point, therefore, pressure will operate in the mass most intensely; there liquefaction will begin; a cavity will be formed in the ice which from its origin will be flattened by the pressure, and therein a minute portion of ice will pass into water. But this water occupies less space than when it was ice. However trifling the difference, the effect is the same as if a slight crack had been formed; the edges of such a crack are weak places, where the pressure must act more intensely because it is not evenly sustained at the point where the water is already formed. For this reason, and also because molecular changes are most easily effected at surfaces where they have already begun, the crack will extend transversely, taking in its course a mass of air-bubbles before held apart by the surrounding ice, but now enabled to unite together by liquid connexion, and sooner or later to escape from their icy prison through some fissure communicating with the outer air. In this manner a vein partly liquid and freer from air than the surrounding ice, is formed, the immediate effect of which is to relieve from pressure the portion of ice at either side, which, therefore, remains unaltered. But, since the whole pressure is not diminished, the relief afforded to some portion of the mass implies an increase of pressure somewhere else, and there, in consequence, a new vein is formed, and so on, until the veins extend as far as the pressure suffices to liquefy portions of the ice. It must, however, be remembered that whatever water is formed in these incipient veins is colder than ordinary ice; the moment that the pressure is removed which alone enables it to maintain its fluid condition, it will return to the state of ice, and then constitute a true blue vein. The foregoing is, we believe, a correct explanation in unscientific language of Tyndall's theory of the veined structure. If not entirely free from difficulties of its own, it so far accounts for the principal phenomena that we have no hesitation in admitting its substantial correctness. An apparent difficulty that occurs to us, though we have not seen it anywhere stated, is this the air which previously existed in the ice has, in some way, been expelled from the blue veins, and to account for this, it was necessary to assume the existence of fissures through which it might make its way; but the same channels would afford a passage to the water formed in the veins, which would escape, and could not therefore freeze again in the place where it was formed. It might be replied that the escape of the confined air, and perhaps of a portion of the water, would so far diminish the pressure on the water remaining in the vein as to cause it immediately to freeze, but we are disposed to think that the process of liquefaction, though essential to the production of the veined structure, is confined to a very small part of the ice. For reasons stated in Professor Tyndall's memoir 'On some Physical Properties of Ice,' it seems certain that in glacier ice exposed to pressure, melting will commence on the inner surface of an air-bubble, and as the minute fissures caused by the repetition of this process on neighbouring bubbles meet each other, fluid connexion will be established between them, and the separated portions of air will be enabled to unite, although the melting may have extended to a very trifling portion of the mass. Should the whole of the water thus formed escape along with the air, the contiguous portions of ice will cohere together in virtue of the property of regelation. Although it has solved the main difficulties of the problem, Tyndall's theory of the origin of the veined structure is not so complete as to leave no room for further inquiry. The best proof of this is the fact that its distinguished author, usually so clear and definite in his language, evinces some hesitation and indistinctness in stating his opinion as to certain points. It is clear, for instance, that he still considers that a mechanical effect of pressure analogous to cleavage, has some share in the production of the structure; but he nowhere explains the precise nature of the changes which he attributes to this cause, nor the evidence of their presence which he has been able to detect in the ice of glaciers. Well-contrived experiments on glacier ice may, doubtless, throw farther light on points that still remain obscure. Pressure, sufficiently great, may probably cause mechanical as well as physical changes*, such as Professor Tyndall has pointed out; but if the pressure requisite for these changes should produce effects which are not traceable in glacier ice, as, for instance, in * It will be understood that, though we use these terms to distinguish modes of action which do not visibly affect the molecular condition of bodies, from those that do so, we do not mean that they are separable by any sharp line of demarcation. They usually own a mutual and complex connexion. 252 Forbes and Tyndall on the Alps and their Glaciers. Jan. the form and disposition of the air-bubbles, it must be inferred that such an amount of pressure has not acted in the glacier. We have now performed the task which we had proposed to ourselves, by setting before our readers an outline of the successive efforts which have led to an understanding of the most important phenomena of glaciers. The subject is very far from being exhausted: even within the limits we have prescribed to ourselves, many details, interesting in themselves, have been omitted, and we have left altogether unnoticed several curious objects of inquiry. In the attempt to trace the progress of our real knowledge of glaciers, as distinguished from imperfect observation and unfertile speculation, it will have been seen that two names have constantly recurred in the preceding pages — those of Forbes and Tyndall. It would be unjust to assert that others are not entitled to some share of merit in the final achievement: Rendu, by just conceptions; Agassiz, by laborious observations; Faraday and Thompson in particular, by discoveries that did not at first appear to bear upon the inquiry; have each had some share in the final achievement. But it remains true that if any one should hereafter inquire by whose labours the knowledge of glacier phenomena and their causes has been gained, the answer must still be Forbes and Tyndall. We have shown, as accurately as we could, the share which each has had in the work; beyond this we decline to draw a comparison, which, if not invidious, would certainly be idle and impertinent. We deprecate that sort of criticism which seems to assume that the wreath that is placed on the brows of one eminent man, must be taken from the head of another who has worked in the same field. The merits of Forbes, and the honour which is his due, are not one whit increased or lessened by the applause that Tyndall may have earned for completing the work which his predecessor had so well begun. We sincerely trust that the differences that have arisen between men whose names are thus inseparably connected may be soon composed. The blows dealt on one side, even though misdirected, were dictated by a generous impulse; those struck in return were urged in self-defence; in such a case there should be no great difficulty in mutual forgiveness. The wisest man, and the truest philosopher, is he who is the first to retire from such a contest, leaving to time to decide the subject in dispute, and afterwards to efface all record of the strife. ART. IX.-1. L'Unité Nationale de l'Italie. Par EMMANUEL MARLIANI, Député. Turin: 1860. 2. Nota del Ministro dell'Interno sull' ordinamento administrativo e finanziario del Regno. Torino: 1860. I1 T is the privilege of few generations to assist at so grand a spectacle as the resurrection of a people and the birth of a new state into the old commonwealth of nations. Such events happen rarely; and still more rarely are they foreseen or deliberately contrived beforehand. They are schemed for by statesmen through long years of anxious vigilance and thought; they are fought for by patriots through long years of defeat, discomfiture, and despair; they are suffered for by captives in squalid dungeons; they are sighed for by exiles in foreign garrets; they form the dream and the prophecy of poets. But time glides on, and brings no apparent approach to the desiderated end; wars pass over the land, and seem only to rivet still faster the chains of the oppressed; insurrections serve but to decimate the noblest votaries of the cause; revolutions give only bewildering gleams and intoxicating draughts of freedom, and servitude settles down again with a gloomier darkness than before;-till a sort of sick hopelessness takes possession even of the most sanguine and most daring spirits. Then, perhaps, comes a combination which no one could have anticipated or effected: events, which would have been powerless if single, become omnipotent when simultaneous and united; the ambition of one man, the restlessness of another, the demented obstinacy of a third, the heroic devotion of a fourth, the opportune advent of the needed statesman, the opportune removal of the insuperable obstacle, join to bring about the moment so long waited for in vain, when the pictured consummation becomes a possible achievement, and the desire of nations' is realised at last. The noblest and wisest of Italian patriots, Daniel Manin, not long before his death, expressed his conviction that another thirty years must pass before Italy could be independent and united, and that the best course for all friends to that great object would be to give up all early hopes and premature attempts, and devote themselves to the work of training the young generation for the task which would devolve upon it. Scarcely more than three years have passed away since Manin was laid in his grave in a foreign land; and the object for which he lived and died is an actual and accomplished, if not yet wholly a completed, fact. We have no intention of dragging our readers through thorny and profitless discussions as to the purity of the agencies and the merits of the agents by which this great result has been brought about. We are concerned with the fact-not with its genesis. Whether the war between France and Austria was unjust or unavoidable; which party prepared, and which began, the conflict; whether Louis Napoleon originally designed, and whether he now relishes, that creation of a Kingdom of United Italy of which he was the undoubted instrument; whether the citizens of the new State ought to be grateful to him for their emancipation and re-union, or to Providence for having overruled his purposes; whether the cession of Savoy and Nice was a moderate and necessary, or a questionable and a needless, price; how far the duplicity and mistatements which undeniably discredited that transaction exceeded the recognised limits of diplomatic mystification; whether Victor Emmanuel and Count Cavour have throughout been actuated by genuine patriotism or by dynastic ambition; whether the invasion of the Neapolitan and Roman territories by the Sardinian army, which was unquestionably a violation of international law, was a violation of international morality as well; or whether the King of Italy, in taking that decided step, did not obey more sacred obligations than those which he transgressed; and, finally, what share in the magnificent success of the joint achievement the judgment of history will assign to the sagacious and compromising statesmanship of Cavour, and what to the lofty and single-souled enthusiasm of Garibaldi,-these are now purely speculative questions upon which we do not care to enter. We have a practical aim in view, and have to deal rather with the present and the future than with the past. We shall assume the consolidation of the various states of the Italian Peninsula into one homogeneous kingdom as a fait accompli, for the purpose of our present argument. It is as yet imperfect indeed, but it may be considered settled. Its completion, too, we may assume as certain, though the time and the mode are as yet buried in obscurity. Two points-and these the only vitally important ones-we hold to be irrevocably determined, partly by diplomatic consent, partly by the inexorable logic of facts'-to borrow a phrase from the imperial vocabulary. First, it is determined that (apart from the utterly anomalous and of necessity temporary occupation of Rome by a French garrison) there is to be no intervention beyond the Alps. England has urged this in the most pertinacious manner and on the strongest grounds of principle. Sardinia has pleaded for it; France professes to consent to it; Austria |