plants, insects, and shells. His name occurs frequently in the Transactions of the Club as the recorder of species new to the district. His health gradually improved, but it was doubtful whether he would be able to bear the strain of any indoor occupation, for which indeed he felt an ever-increasing aversion.

It was the time of the discovery of gold in Australia, and after much discussion he and his elder brother joined the stream of adventurers and sailed in 1852 for Victoria. In this rough" school of mines " he acquired that insight into the building-up of the earth's crust and that practical knowledge of minerals which served him so well in afterlife as a mining engineer. But although the whole colony

was in the grip of the gold-fever, Belt retained the same quiet habits of observation which had marked him at home-for there, as to whatever part of the world his work subsequently called him, the engineer was always at heart a naturalist. He proved an excellent observer, and a certain speculative tendency led him to group his observations so as to bring out their full theoretical bearing.

Amid real hard work he found time to evolve a theory of whirlwinds and to speculate upon the soaring of birds. A companion has recorded in the following terms another matter which engaged much of his attention at this time: "The boldest of his speculations, and one of the soundest, as after-events proved, was his plan for crossing the Australian continent. He proposed, at the time the government expedition was mooted, to replace the costly plans of the government by the following scheme:-That he and his brother Anthony (who was unfortunately lost in the Royal Charter) should be conveyed to the Gulf of Carpentaria, with about twenty pack-horses loaded with provisions and water; that an escort should protect them for some twenty miles from the coast, and that then the two voyagers only, with their pack-horses, should make their way to Cooper's Creek, the farthest known accessible point from the Victorian settled districts. Belt argued justly: 'If we fail, only two lives will be lost, but all chances are in our favour; we are provided with water and food more than ample to cover the distance we have to travel. Every step of our road carries us homeward and to safety. If we never find a drop of water on the road, our animals have

enough to carry those who have to bear the whole journey to their goal, and as the animals succumb they will be shot or turned adrift.' The event showed Belt's sagacity. The unfortunate government expedition left Melbourne loaded with camp-followers and impedimenta, and by the time they reached a few stages beyond Cooper's Creek were well-nigh exhausted. Burke, the leader of the expedition, in desperation started with his two men, Wills and King, and bravely struck out for the Gulf of Carpentaria. Through desert and fertile plains, not altogether destitute of water, they reached in safety the northern shore of Australia; but the energy, the courage, and the strength that took them this long, weary journey did not suffice to carry them back over double the distance to their camp. Brave hearts! they struggled on; but King only, and as a worn-out man, ever saw Cooper's Creek again, Belt's plan would have solved the problem without loss of life and at a tenth of the cost." He always regretted that he had not the means of carrying it out independently of government assistance.

After eight years in Australia Belt returned to England, married, and was successively manager of mining companies in Nova Scotia, North Wales, and Nicaragua, sandwiching in between these appointments a visit to Brazil to report upon some gold mines in the province of Maranham. In whatever part of the world his work took him he turned for rest and relaxation to the branches of natural science for which the locality offered the greatest opportunity.

In Nova Scotia he began those investigations into the cause and phenomena of the glacial period which were to be the study of the last years of his life, and to which he himself attached the greatest importance. In Wales he took up the question of the age of the rocks in the neighbourhood of Dolgelly, and after much study of their fossils proposed the now accepted classification of the Lingula flags of the Lower Silurian system into the Maenturog flags and slates, the Festiniog flags, and the Dolgelly slates. The collecting of lepidoptera was his chief amusement in Brazil, where he made his first acquaintance with the teaming life of the torrid zone and laid the foundation for those observations on tropical nature which his longer stay in Nicaragua gave rise to, and which are recorded in this book.

After his return from Central America, his services were in great request as a consulting mining engineer, and the succeeding years of his life were spent in almost continual travel: over all parts of Great Britain, to North and South Russia, Siberia, the Kirghiz Steppes, Mexico, and the United States. It was on one of his annual visits to Colorado that he was seized with sudden sickness and died on September 21, 1878, at the early age of forty-five.

Thomas Belt was an accurate and intelligent observer possessed of the valuable faculty of wonder at whatever is new or strange or beautiful in nature, and the equally valuable habit of seeking a reason for all he saw. Having found or imagined one, he went on to make fresh observations, and sought out new facts to see how they accorded with his supposed cause of the phenomena. The Naturalist in Nicaragua has therefore a value and a charm quite independent of the particular district it describes. As a mere book of travel it is surpassed by scores of other works. The country and the people of Nicaragua are too much like other parts of tropical Spanish America, with their dull, lazy inhabitants, to possess any novelty. There is little in the book that can be called adventure, and still less of geographical discovery.

And yet, the many and highly diversified phases in which life presents itself in the tropics enabled the skilled naturalist to fill a volume with a series of episodes, experiences, and speculations of which the reader will never tire. His keen powers of observation and active intellect were applied to various branches of scientific inquiry with unflagging ardour; and he had the faculty of putting the results of these inquiries in a clear, direct form, rendered the more attractive by its simplicity and absence of any effort at fine writing. He does not obtrude his own personality, and, like all genuine men, he forgets "self" over his subject. Instead of informing us whether or not he received the salary of an ambassador and the treatment of a gentleman," he scatters before us, broadcast, facts interesting and novel, valuable hints for future research, and generalisations which amply repay a close study. Not alone the zoologist, the botanist, the geologist, but the antiquarian, the ethnologist, the social philosopher, and the

meteorologist will each find in these pages additions to his store of knowledge and abundant material for study.

With all this, the work is not a mere catalogue of dry facts: it is eminently a readable book, bringing vividly before us the various subjects with which it is concerned. Minutely accurate in his description of facts and bold in his reasoning upon them, Belt covered so much ground that some of his theories have not held their own; but others have stood the test of time and been absorbed into the world's stock of knowledge, while all bear witness to the singular grasp of his mind and have stimulated thought and observation-which is a great virtue in theories, be they true or false.

It has been already stated that Belt devoted the scanty leisure of his last years to the study of the glacial period, entering with zest into the consideration of its cause, the method of deposition of its beds, and the time-relationship of man to it-complex questions on which his imagination had full scope, and which, had his life been prolonged, his patient accumulation of evidence might have ultimately led him to suggest answers that would have been generally accepted by scientific men. But the cause of the remarkable change of climate during those late Tertiary and postTertiary times known as the glacial period is still without a completely satisfactory explanation. In Belt's day geologists were inclined to get over the difficulty of accounting for the phenomena by any feasible terrestrial change by explaining them as the result of cosmical causes, and Croll's theory of the increase of the eccentricity of the earth's orbit was widely received among them. Belt, on the other hand, held that the cold was due to an increase in the obliquity of the ecliptic. But these astronomical explanations have not met with much acceptance by physicists; and so chemists have been turned to by some geologists for support of the hypothesis of the variation in the amount of carbon dioxide in the air, or of other alterations in the atmosphere, while others have gone back to the idea of geographical changes. That considerable oscillations of the relative levels of land and sea took place during the Ice Age has been now clearly established, and the general result of the investigations favours Belt's opinion that the land during part of that period

stood much higher than now over the northern regions of Europe and North America. It would, however, lead us too far away from the present book to enter into even a cursory examination of his views upon the glacial period, and those readers who desire to pursue the matter will find assistance for doing so in the bibliography at the end of this Introduction.

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Of more immediate interest to us are the observations on animals and plants in reference to the theory of evolution of living forms" which the title-page announces as a part of the narrative, and which indeed form the main portion of the work. Upon the publication of Darwin's Origin of Species in 1859, Belt had become an ardent evolutionist, and was henceforth always on the look-out for facts in support of the theories which had breathed such new life into biological studies. In Nicaragua he devoted special attention to those wonderful protective resemblances, especially among insects, which Bates had explained by his theory of " Mimicry; " and as the subject crops up again and again in this book, the non-scientific reader will find it helpful to have before him an outline of the expanded and completed theory-though he should be warned that some writers have been too much inclined to attribute to "mimicry any accidental resemblance between two specics. How far such accidental resemblances may be carried is probably well illustrated by the bee, the spider, and the fly orchis of our own downs and copses.

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'Mimicry proper is often confused with protective resemblance," and it will be advisable to begin with the consideration of the latter.

Concealment, while useful at times to all animals, is absolutely essential to some; and it is wonderful in what different ways it is attained. In cases of cryptic resemblance to surroundings " the shape, colouration, or markings are such as to conceal an animal by rendering it difficult to distinguish from its immediate environment. In most cases the effect is protective; but in snakes, spiders, mantids, and other preying animals it is termed aggressive, since it enables these animals to stalk their prey undetected. It is probable that this power, when possessed by a vertebrate animal, nearly always bears the double meaning, as in the green tree frog, where the colouration is protective