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De. Hartwig has shown himself a very clever compiler of popular scientific works, and the present is perhaps the best he has produced. The “Polar World” has always excited a charm over the minds of maritime nations, and the lovers of adventure in strange countries. The varied forms of icebergs gleaming in the auroral coruscations of the long night of the Arctic regions, the temperature so low that mercury solidifies, the huge wastes of trackless snow, the warmer portions with open water, the homes of the walrus, the white bear, the whale, the grampus, and the auks—these, together with the vegetation, so different from that of temperate regions, all contribute to a series of pictures, well represented in Dr. Hartwig's pages, and on which young and old may dwell with curiosity and delight.

It is not latitude alone that determines the arctic character of a given region; as the climate is affected by the relative dispositions of land and sea, by the influence of the warm Gulf-stream currents, and by the positions of mountain ranges and their heights. After passing from the colder temperate lands to the polar zones, two distinctly characteristic regions will be observed—that of “the forest, and that of the treeless wastes. The latter, comprising the islands within the Arctic circle, form a belt, more or less broad, bounded by continental shores of the North Polar Seas, and gradually merging, towards the south, into the forest region, which encircles them with a garland of evergreen Coniferæ.” When trees cease, mosses and lichens form the chief vegetation, and " in winter, when animal life has mostly retreated to the south, or sought refuge in burrows and in caves, an awful silence, interrupted only by the hooting of a snow owl or the yelping of a fox, reigns over their vast expanse.” With the spring and summer, numerous flights of birds appear, and the coasts swarm with fish, gnats abound in the swamps, and the scene is enlivened by flowering plants.

The “treeless zone of Europe, Asia, and America occupies a larger space than the whole of Europe. Even the African Sahara and the Pampas of South America are inferior in extent to the Siberian Tundri.” Still larger are the forest regions, frequently

* “The Polar. World : a Popular Description of Man and Nature in the Arctic and Antarctic Regions of the Globe.” By Dr. G. Hartwig, author of "The Sea and its Living Wonders ;” “The Harmonies of Nature;" "The Tropical World ;" etc. With eight Chromo-sylographic Plates, three Maps, and numerous Woodcuts. Longmans.

The birch grows

monotonous from the prevalence of the Coniferæ, but varied in certain districts by birch and dwarf willows. farther north than the pines and firs can follow; and the willow makes its fight for life against adverse conditions, until it is reduced to a little shrub. Many valuable timber trees belong to the milder portions of the Arctic regions, and our plantations and gardens are enriched by arctic species of pinus, abies, picea, etc.

The power of the human frame to accommodate itself to the intense cold of the Polar circle is truly wonderful. Kane experienced a temperature so low, that chloric ether became solid, and the mean of his best spirit thermometers registered -68o and -100° below the freezing point of water. Not only natives, but travellers, soon grow accustomed to the great cold. They get hungry, consume great quantities of fat food, and maintain their animal heat with surprisingly little suffering. Dr. Hartwig cites Kane's account of Petersen, who lived for two years at Upernavik, and seldom entered a room with a fire; and of George Riley, who could sleep comfortably on sledge journeys with no other cover than a walkingsuit, although the temperature was —30°. The average immunity from disease, and general safety of Arctic expeditions, made the conduct of our Government in doing so little for the rescue of Franklin all the more blameable. A few months on an African or West Indian station are far more perilous than a sojourn in Arctic regions of much longer duration.

Dr. Hartwig has culled from Arctic voyagers many interesting accounts of icebergs, ice floes, etc., and has adorned his book with beautiful plates of these wonders of the Polar zone ; and it is necessary to familiarize the mind with their vast dimensions to enable us to understand the important action which ice had in former ages in forming and shaping many of the strata in our country, deposited or modified, when our climate was much more severe.

A single stranded iceberg, roughly measured by Dr. Hayes, was estimated to contain 27,000 millions of cubic feet, and to weigh 2,000 millions of tons. Another stranded iceberg, seen by Ross, was 4,167 yards long, 3,689 yards broad, and 51 feet high above the level of the sea. This monster was estimated at 1,292,397,673 tons ! Many of these monster icebergs come down to the sea from Polar rivers and glaciers, bringing with them prodigious quantities of earthy matter. Tindall Glacier has two miles of sea front, and Humboldt Glacier, connecting Greenland with Washington Land, stands up 300 feet above the sea, and extends for sixty miles from Cape Agassiz to Cape Forbes.

When exposed to warmer air or a warmer water current, icebergs become very brittle, and “Scoresby relates the adventure of two sailors who were attempting to fix an anchor to a berg. They began to hew a hole in the ice, but scarcely had the first blow been struck when suddenly the immense mass split from top to bottom and fell asunder, and the two halves falling in contrary directions with a prodigious crash.”

In the “Polar World” will be found descriptions of the various Arctic races, Laps, Samoyedes, Ostjaks, Jakuts, Tungusi, Esquimaux, etc., compiled in a pleasant way from a great number of sources. The Jakuts (of Siberia) are stated to be remarkable for their sharpness of sight, and a curious instance is mentioned of one of them pointing to Jupiter, and telling Lieut. Anjou that “he had often seen yonder blue star devour a smaller one, and then after a time cast it out again.” He must have seen the first and last stages of the transit of a satellite, a feat which may have been performed in other places, as astronomical works mention several cases of persons able to see the larger satellites with the naked eye.

Arctic life requires ample digestive powers, and the heat necessary for existence can only be maintained by a large consumption of what Liebig terms the respiratory elements. In illustration of this, Dr. Hartwig cites Captain Parry, who, as a matter of curiosity, once tried how much an Esquimaux would eat. In twenty-four hours he consumed 4} lbs. of frozen sea-horse flesh, and the same quantity boiled, together with one pound twelve ounces "bread and bread dust." To these solids, weighing 101 lbs., he added a pint and a quarter of rich soup, three rim glasses of strong spirits, a tumbler of strong grog, and one gallon and one pint of water, nor did he deem this supply at all extraordinary in quantity.

After describing the chief expeditions to the northern Polar regions, including the disastrous one of Sir John Franklin, and those in search of him, Dr. Hartwig turns to the Southern Pole, with which our acquaintance is very limited. Sir James Ross, surmounting the most awful perils, managed to reach lat. 78° 11 S., and found the way blocked by prodigious coast walls of ice. In 77° 5 S. he saw Mount Erebus in magnificent eruption, and since his voyage no one has ventured to explore the mysteries of the Antarctic Pole.

As a book of pleasant reading, beautifully illustrated, and handsomely printed, “ The Polar World” deserves, and will command, a high place.



In introducing the woodcuts, omitted from No.12 of THE STUDENT, representing the form in which the pure China-clay, or kaolinite, is seen to occur when examined under the microscope, we may give a few additional particulars of the history of the mine which was the subject of our notice.

In a survey of the manor of Treverbyn (in which this mine is situate) made in the 44th year of Queen Elizabeth, it is spoken of as a “very good tynworke called Carcles," while in another survey made during the same reign, it is called “ Crikelase Tynworke.” Later on, in the time of the Commonwealth, we read of the Mannor of Treverbin Courtney, with y rights, members, and appurtenances scituate, lying, and being in yo County of Cornwall, pte of ye annexed Duchy there, and pcell of yo possessions of Charles Stewart, late Duke of Cornewall, but now settled on trusts for the use of ye comon-wealth.” Further on, mention is made of Carclaze as a good, “Tinne Worke knowne by yo name of Crucke-glasse.”

In our former notice of this mine we alluded to the existence of adits or tunnels in the side of the excavation. When Carclaze was worked wholly for tin, the ore was conveyed through one of these tunnels more than half a mile in length to the mills below to be stamped. Flat-bottomed boats were sent by this subterranean canal laden with the rough ore. The present lessees, in opening up this old adit or tunnel, which had in some places fallen in, came upon several of the boats formerly used for the carriage of the tin ore. We

may add that from four to five thousand tons of China-clay, worth about £l per ton, are now annually obtained from this pit, and from a material that was once washed away as rubbish.


INDIA-RUBBER T'UBING.—Ordinary vulcanized india-rubber tubing becomes saturated with gas, which again evaporates at its outer surface, causing a most disagreeable smell. An invention for the prevention of this, by coating the india-rubber tubing with a varnish, has been patented. The chief novelty in it is that the varnish is easily made, and it renders the substance of the tube impervious to gases. This varnish is composed of linseed oil, fine litharge, or white lead, in the proportion of one quart of oil to one pound of litharge. These substances should be well boiled together until brought to a proper thickness or body, and while hot the composition is applied by running it through the tube to be coated or lined. The varnish for the outside is made by mixing one quart of linseed oil with half a pound of litharge, and by adding to the same about a gill of gold size, these ingredients should be well boiled together, and while hot should be applied with a brush or a sponge.

INDIA-RUBBER SOLES FOR BOOTS AND SHOES.- Mr. F. J. Mayall, the inventor of the process just described, has also patented a method of making india-rubber soles for boots, etc. He applies to a linen cloth india-rubber dissolved in naphtha, camphine, or other suitable solvent. With this india-rubber solution he mixes whiting, sulphur, litharge, or white lead, calcined magnesia, lampblack, and clay, in the following proportions.-Four pounds of rubber, two pounds of whiting, one pound of sulphur, one pound of litharge, one half-pound of magnesia, one halfpound of lampblack, and two pounds of clay. When sufficient of this compound has been applied to the cloth, it is passed between rollers, the surface being sprinkled with French chalk to prevent adhesion. Patterns can be imprinted in this manner by the use of an impression cloth, or the surface can be simply roughened. The sheet should be exposed for three hours and a half to a temperature of 60° Fah. The impression cloth is then removed from the surface of the india-rubber. The cloth on which the india-rubber was first spread can be removed, by moistening it with warm water, naphtha, or camphine. The sheet of prepared rubber can be then cut into any desired forms.

REDUCING ALUMINUM FROM ITS Ores.—Mr. A. L. Fleury, of Boston, U.S., has patented the following method of extracting aluminum. He mixes pure alumina with gas-tar, resin, petroleum, or some such substance, making it into a stiff paste, which is divided into pellets; and these pellets or balls are dried in a drying oven, then placed in a strong tube or retort, which is lined with a coating of plumbago. They are then exposed to a cherry-red heat. The retort must be sufficiently strong to stand a pressure of from 25 to 30 pounds on the square inch, and be so arranged that, by means of a safety-valve or tube, the necessary amount of hydro-carbon gas can be introduced into the retort among the heated mixture, and the pressure of from 20 to 30 pounds on the inch be main

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