where it might now be sought in vain. Perhaps, however, the decrease of our choicer native ferns may be due not so much to the rapacity of cultivators as to the increasing pollution of the atmosphere in many parts of the country. Air fraught with coal-smoke is very uncongenial to many ferns and mosses, and checks their fructification.

In recommending this book to all who are interested in the study and in the cultivation of ferns, we must beg to express our sympathy with the author, who has been deprived of that sense which to all observers of Nature is dearer than life itself.

Narrative of the North Polar Expedition. U.S. Ship Polaris, Capt. C. F. Hall commanding. Edited by Rear-Admiral C. H. DAVIS, U.S.N. Washington: Government PrintingOffice.

POLAR exploration excites in men of different tastes and pursuits. a widely different amount of interest. The biologist looks on almost with indifference, well knowing that a year's labour in the far north would yield fewer results of value than might be met with in a single day in climates more genial. The geologist and mineralogist, though well aware that important portions of the "great stone book" have been, in all probability, deposited around the poles, still fear that accumulations of ice and snow may for ever hide them from human perusal. On the other hand, the geographer, the meteorologist, and the student of terrestrial physics turn their gaze northwards with eager curiosity, and will doubtless never desist from their endeavours to solve the mystery of the poles till their efforts are crowned with success, or till many future adventurers, like Franklin and Hall, have found a glorious death. Nor can the risk and the possible sacrifice be considered to outweigh the prize that remains to be won. Material benefit, indeed, is out of the question. No one now explores the icy regions in the hope of finding an available passage from Europe, or from the eastern shores of North America to the Pacific; nor is the prospect of mineral wealth a temptation, for though valuable ores doubtless lie hid in these regions, the cost and difficulty of bringing them to daylight and transporting them to a market would be scarcely surmountable. But from a speculative point of view the inducements to polar investigations are tempting indeed. Setting aside the extravagant dreams of earlier days, such as the notion of an aperture leading down to beautiful and habitable regions in the interior of our globe, it remains to be decided whether the poles are covered, according to the theories of Adhémar and others, with massive caps of ice miles in thickness; whether they are, as some suppose, covered by open sea, enjoying a milder climate than the

regions immediately around them; or whether they are utterly undistinguished by any physical feature from the arctic wastes already explored. At present we can only infer, with more or less probability, as to what may be the condition of the earth at the extremity of its axis, and with this uncertainty we cannot feel satisfied.

Among the many who have sought to solve the "mystery of the Pole none can claim a higher place than Capt. Charles Francis Hall, who, if merit could command success, might well have hoped to plant the flag of his country on the most northern part of the globe. He belonged to a class of men for whom we entertain a particular admiration. Like all true specialists, he had devoted his whole being to the solution of one question. For this he had thought, and studied, and prepared himself in every possible way, so that when the crowning opportunity came he might not be found wanting. To this end he sought to stir up public opinion in favour of a polar expedition under national auspices. He lectured in various cities of the Union; he corresponded with official personages, and, in short, left no stone unturned towards the completion of his chosen task. This part of Capt. Hall's life, indeed, reminds us of the journeys of Columbus when he went from court to court soliciting the means to put his project into execution. In pure, self-forgetting devotion to a great idea these two explorers are singularly alike. The American, however, unlike the Genoese, had to deal with a Government which honours and appreciates Science.

The work before us-whilst it recounts the progress of the Expedition, the illness and the lamented death of Capt. Hall, and the heroic struggles of the party after his end-does not detail the scientific results of the Expedition. The various journals and reports in which the observations made by the Expedition lie scattered have not yet been completely digested. Some of the documents, as well as of the specimens collected, appear to have been lost when the Polaris had to be abandoned. Many interesting facts, however, are recorded in these pages. Those who imagine that mosquitoes are an exclusive feature of tropical climates will perhaps be surprised to learn that these pests, along with other two-winged flies, haunt even the far north. Two caterpillars were also found among moss, but of what kind it is not stated. The Mammalia of the region explored consist chiefly of musk-oxen, foxes, seals, lemmings, bears, wolves, and walruses. The Expedition therefore, though it approached the boundaries of animal life, did not actually cross them, as Captain Nares and his followers seem to have done. The fauna and the flora of the two Expeditions, when published, will be welcome as a contribution to our knowledge of the geographical distribution of organic life.

A curious physical fact recorded is the freezing of kerosene oil, which hydrocarbon at 44° F. assumed a consistence like that of

melting wax, and a milk-white colour. No appearance of crystallisation was detected, even under the microscope.

There is one lesson to be drawn from this book which should on no account be overlooked. Copies of the "Narrative " have been forwarded, gratuitously and unsolicited, to universities, to learned societies, and public libraries, as well as to scientific journalists like ourselves, over the whole civilised world. By such acts of munificence the Government of the United States sets an example to its neighbours which we are sorry to see finds but very scanty imitation. Will England ever learn to " Americanise her institutions" in this respect?

Scepticism in Geology, and the Reasons for it. By VERIFIER. London: John Murray.

To this book a preliminary objection may be taken, serious, if not absolutely fatal. The author's ostensible position, as declared in his title and in his preface, is that of the sceptic-using the word of course in its philosophical and only legitimate sense. He selects as his motto the "Ama nesciri" of Thomas à Kempis. He calls for more thorough demonstration than geologists have in his opinion been able to furnish hitherto in support of their theories. Far be it from us to question his right to assume such an attitude, provided it be done really and consistently. Like every other science, Geology must be prepared to submit her conclusions to full and impartial criticism. She can claim our assent merely on condition of producing valid evidence. But what is scepticism? It is the dismissal of all preconceived notions bearing upon the question at issue; the refusal to accept without proof any proposition whatever, joined to complete indifference what conclusion may be arrived at provided it be in accordance with the logical interpretation of established facts. To give a familiar illustration, it is the frame of mind which the judge often explicitly enjoins the jurymen in cases which have excited a considerable amount of public feeling. They are told to dismiss all prejudices either for or against the prisoner, and utterly to ignore everything save the evidence which has been presented to them This is true scepticism. But there is a pseudo-scepticism, very common among the opponents of what are called "modern scientific theories," which is combined with the grossest credulity, and which is in fact merely a consequence of the latter feeling. John Nokes doubts very strongly that a = b, and considers that in calling for additional evidence he is assuming the position of a sceptic. But what if all his doubts spring merely from a strong preconceived notion-not, let us bear in mind, resting upon any evidence-that a is not equal to b? He is then no sceptic, but a dogmatist in disguise. Such, we are sorry to

find is the real position of "Verifier." His mind, in approaching the question, is not "tabula rasa," but is filled with prepossessions and with an anti-geological-we can scarcely help saying utterly unscientific-dogmatism, which the work before us is an attempt to justify. "The assumptions of modern geology," he tells us, "have filled some minds with alarm." But alarm, or indeed emotion of any kind, is utterly to be avoided by the man who lays claim to the position of a sceptic.

It may seem that we have brought grave charges against the unknown author, but on a careful examination of the book they will appear only too fully justified. He seems to anticipate "rough usage," if noticed at all, possibly from some internal misgivings concerning his "facts" and his " arguments," but, as is common with writers of his school, he appeals to the "candid reader."

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Our first proof that he is by no means the disinterested doubter, the modest enquirer he would fain appear, may be found in his remarks on geological time. He tells us "it is necessary to protest against the insatiable demands of geologists for time." He sneers at the observation of Darwin that it cost only 300 millions of years to denude the Weald. He declares there cannot be a more groundless assumption " than the dictum of Mr. Geikie that time is power." Can he pretend to misunderstand Mr. Geikie's meaning? "Would it not," he asks," become the geologists of our time to abandon a position which enforces on their followers a belief almost amounting to a superstition ?" Now we defy him to show any inherent or intrinsic improbability in the "untold ages," the "incalculable periods of time" which move his indignation. A priori, it is equally likely that the world has existed for six thousand, six million, or six billion years, and those who suppose the latter are not more credulous than those, if any, who still believe the latter. The advocates of Usher's chronology, who dream that "the world was created in autumn, 4004 years before the vulgar Christian era," have certainly no reason to tax geologists with credulity or superstition. Our argument in favour of the long past duration of the earth is drawn from the impossibility of compressing into a shorter time the occurrences of which the "stone book" has preserved the record. His grounds against the "incalculable ages" are never put forward at all, and may therefore, without any want of charity, be set down as a mere preju. dice. It is instructive to note how eagerly, in default of any facts to prove the recent origin of the earth, he catches at shadows. He tells us in his Preface-" Darwin, Lyell, and others who proclaim a term of 300 millions of years insufficient for some of the operations of geology, are warned- So much the worse for geology, since physical conditions render it impossible to allow her more than 10 or 15 millions of years.'" But does he not know that we regard these "physical considerations "-the recently attempted mathematical investigations into the maximum

age of the earth-as scarcely worth the paper upon which they are written? Mathematical demonstration is irresistible when applied to abstractions, but when it seeks to deal with realities it is often vitiated by being based upon false, or at best groundless, premises. The question is quietly and adroitly begged in such expressions as "Let us suppose, If we only assume," &c., and the public-dazzled and awed by the display of formula-never look beneath at the flimsy foundation.

But the lingering belief in the recent origin of our earth is not his only prepossession. Towards the end of the work he declares his belief that the earth has not reached its present condition, but has been finished off at once according to specification, like a contract job-if we may be allowed the comparison-by a First Cause, acting directly and from without! Because the "scientific mind "-which his own is apparently not-repudiates an assumption so degrading, so unworthy of Deity, it is charged with a stubborn resistance to the belief in a FIRST CAUSE." Can he fail to see that if such be the origin and the earlier history of the earth, the very existence of geology is destroyed? But let us quote some of the passages in which he places his antiscientific creed in the fullest daylight :-" One vast fallacy would appear to underlie the doctrine of Modern Causes, the supposition that the world we inhabit-so beautiful, so pregnant with every gift which can contribute to man's progress, prosperity, and happiness-has been turned out by its Maker unfinished and imperfect; that it is capable of improvement, at least of development, and is undergoing material change day by day." "Is there any inconsistency in supposing that when a potter moulds a vase out of a lump of clay he should put forth his greatest energy and exert his utmost skill to finish it and turn it out perfect? That the work of the creation of the earth was one of perfection defies all disproof. What need, then, to imagine that it was done by little and little? least of all can we admit a solution of the problem of cosmogony, involving the absurdity that the work was left unfinished and needs constant alteration by means of certain mechanical self-acting operations. We venture to hope that the more geology is studied in an earnest spirit, free from the mirage of attractive but shadowy hypotheses, the more it will be acknowledged that not blind force, however gentle, nor mechanical impulses, however gradual, rendered our planet what we find it. It will eventually be acknowledged that at the time and in the process of fashioning the globe, a power was exerted totally different from the present course of nature." Here, then, the secret is revealed. The author's real difficulties in the way of accepting the truths of geology are his preconceptions of what is an absurdity," of what is "perfection," and of how, in his opinion, the "First Cause" ought to have worked! With a man who can seriously maintain that the channels of rivers were made for them and not by them, it is impossible to argue. Had he been