and up through into Behring's Straits. Upon all these last-mentioned right whale grounds there is good fishing from May to September, inclusive.

I have not as yet found the log-book of any whaler that has cruised here at any other season of the year, and, therefore, my information as to the rest of the year is negative.

But there is reason afforded by the chart for the opinion that the right whales of the North Pacific never come to the South of the parallels named, and that, therefore, as a general rule, these fish remain somewhere to the North of the parallel of 35° all the year. If this indication of the chart be correct, and I see no reason to question it, it appears that this animal must have supplies of food all the year round above 35° N.

I have reason to believe that the temperature of the sea has much to do with the whale, or the growth of its food; that the sperm whale delights in warm water, and the right whale in cold; and those whalemen who are co-operating with me in collecting materials for the "Wind and Current Charts," and the whale chart belongs to the series, will, therefore, understand and appreciate the importance of keeping a daily record as to the temperature of air and water.

There is another point, also, to which I would call their attention, because, by regarding it, it may prove of value to these researches and to them, and that point is deep sea soundings. It is said that the sperm whale goes to the bottom of the sea for its food. What is the greatest depth to which it can go for this purpose? and are its places of resort confined to parts of the ocean that come within these depths ?

Now, if owners would provide their ships each with a few thousand fathoms of twine, and some scraps of old iron or lead to serve as sounding weights, I am sure that the whalemen, from the great philosophical interest which many of them manifest with regard to my researches, would in calms get deep sea soundings for me.

If the ocean were very deep, and the time could not be spared to haul up the line, it might, the length out being known by what is left, be cut; and as the line and sinker would cost but little, the expense to each ship would be but a trifle.

I take this occasion to say, because some of the whalemen have supposed it unnecessary to continue the abstract when in sight of land, that it is important to have a complete abstract for every day they are at sea, that we may know whether they find fish or not, how plentifully, the force and direction of winds and currents, temperature of the air and water, and glean information as to all other phenomena which they are requested in the abstract log to note.

V.-BICHE DE MAR, OR SEA SLUG.

The animal belongs to the genus Holothuria, and the prepared article finds a ready sale in the China market, where it is used as an ingredient in rich soups. Of the biche de mar there are several kinds, some of which are much superior in quality to the others: they are distinguishable both by shape and colour, but more particularly by the latter. One of the inferior kinds is slender, and of a dark brown colour, soft to the touch, and leaves a red stain on the hands; another is of a gray colour, and speckled; a third is large and dark yellow, with a rough skin and tubercles on its sides. The second kind is often eaten raw by the natives. The valuable sorts are six in number: one of a dark red colour; a second is black, from 2 inches to 9 inches in length, and its surface, when cured, resembles crape; a third kind is large, and of a dark gray colour, which, when cured, becomes a dirty white; the fourth resembles the third, except in colour, which is a dark brown; the fifth variety is of a dirty white colour, with tubercles on its sides, and retains its colour when cured; the sixth is red, prickly, and of a different shape and larger size than the others; when cured it becomes dark.

The most esteemed kinds are found on the reefs, in water from 1 to 2 fathoms in depth, where they are caught by diving. The inferior sorts are found on reefs which are dry, or nearly so, at low water, where they are picked up by the natives. The natives also fish the biche de mar on rocky coral bottoms, by the light of the moon or of torches; for the animals

keep themselves drawn up in holes in the sand or rocks by day, and come forth by night to feed, when they may be taken in great quantities. The motions of the animal resemble those of a caterpillar, and it feeds by suction, drawing in with its food much fine coral, and some small shells.

Capt. Eagleston stated, that the biche de mar is found in greatest abundance on reefs composed of a mixture of sand and coral. The animal is rare on the southern side of any of the islands, and the most lucrative fisheries are on the northern side, particularly on that of Vanua-Levu, between Anganga and Druau. In this place the most frequent kind is that which resembles crape. In some places the animal multiplies very fast, but there are others where, although ten years have elapsed since they were last fished, none are yet to be found.

The biche de mar requires a large building to dry it in. That erected by Capt. Eagleston, on the Island of Favea, is 85 feet long, about 15 or 20 feet wide, and nearly as much in height. The roof has a double pitch, falling, on each side of the ridge, to eaves which are about 5 feet from the ground. The roof is well thatched, and ought to be perfectly water-tight. There are usually three doors, one at each end, and one in the middle of one of the sides. Throughout the whole length of the building is a row of double-staging, called batters, on which reeds are laid.

On the construction of this staging much of the success of the business depends. It ought to be supported on firm posts, to which the string-pieces should be well secured by lashing. The lower batter is about 4 feet from the ground, and the upper from 2 to 3 feet above it. Their breadth is from 12 to 14 feet. Upon the large reeds with which the batters are covered is laid the "fish-fence," which is made by weaving or tying small cords together. This is composed of many pieces, the height of each of which is equal to the breadth of the

batter.

A trench is dug under the whole length of the batters, in which a slow fire is kept up by natives, under the direction of one of the mates of the vessel. The earth from the trench is thrown against the sides of the house, which are at least 2 or 3 feet from the nearest batter, in order to prevent accident from fire. This is liable to occur, not only by carelessness, but from design on the part of the natives. As a further precaution, barrels filled with water are placed about 8 feet apart, along both sides of the batters.

After the house has been used for about a week, it becomes very liable to take fire, consequence of the drying and breaking of the material used in the lashing. In this case it is hardly possible to save any part of the building or its contents. To prevent the falling of the stages by the breaking of the lashings, fresh pieces of cordage are always kept at hand to replace those that are charred, and show signs of becoming weak. A constant watch must be kept up night and day, and it requires about fifteen hands to do the ordinary

work of a house.

The fires are usually extinguished once in twenty-four hours; and the time chosen for this purpose is at daylight. The fish are now removed from the lower to the upper batter, and a fresh supply introduced in their place. This operation, in consequence of the heat of the batter, is hard and laborious; and fifty or sixty natives are usually employed in it.

Firewood is, of course, an important article in this process, each picul of biche de mar requiring about half a cord to cure it. This fuel is purchased of the chiefs, who agree to furnish a certain quantity for a stipulated compensation. As much as twenty cords are sometimes bought for a single musket. In carrying on the drying it is important that the doors be kept shut while the fires are burning. Much also depends upon the location of the house, whose length should be at right angles to the course of the prevailing winds

The batters also should be nearest to the lee side of the house.

Before beginning the fishery, the service of some chief is secured, who undertakes to cause the house to be built, and sets his dependents at work to fish the biche de mar. The price is usually a whale's tooth for a hogshead of the animals, just as they are taken on the

reef. It is also bought with muskets, powder, balls, vermilion, paint, axes, hatchets, beads, knives, scissors, chisels, plane-irons, gouges, fish-hooks, small glasses, flints, cotton cloths, chests, trunks, &c. Of beads, in assorted colours, the blue are preferred, and cotton cloth of the same colour is in most demand. For one musket a cask, containing from 130 to 160 gallons, has been filled ten times. When the animals are brought on shore, they are measured into bins, where they remain until the next day. These bins are formed by digging a trench in the ground, about two feet in depth, and working up the sides with cocoa-nut logs until they are large enough to contain forty or fifty hogsheads. If the fishery is successful two of these may be needed. Near the bins are placed the trade-house and trade-stand. In the first the articles with which the fish is purchased are kept, and in the second the officer in charge of them sits, attended by a trusty and watchful seaman. The stand is elevated, so that the persons in it may have an opportunity of seeing all that is taking place around them. All the fish are thrown into the bin before they are paid for. In these bins the fish undergo the operations of draining and purging, or ejecting their entrails. These, in some of the species, resemble pills, in others look like worms, and are as long as the animals themselves.

The larger kinds are then cut along the belly for a length of three or four inches, which makes them cure more rapidly, but care must be taken to avoid cutting too deep, as this would cause the fish to spread open, which would diminish the value in the market.

When taken out of the bins and cut, the fish are thrown into the boilers, which are large pots, of which each establishment has five or six. These pots have the form of sugar boilers, with broad brims, and contain from 100 to 150 gallons. They are built in row in rude walls of stone and mud, about two feet apart, and have sufficient space beneath them for a large fire. The workmen stand on the walls to fill and empty the pots, and have within reach a platform, on which the fish is put after it has been boiled. It requires two men to attend each pot, who relieve each other, so that the work may go on night and day. They are provided with skimmers and ladles, as well as fire-hooks, hoes, and shovels. No water is put into the pot, for the fish yield moisture enough to prevent burning. The boiling occupies from twenty-five to fifty minutes, and the fish remain about an hour on the platform to drain, after which it is taken to the house and laid to a depth of four inches upon the lower batter. Thence at the end of twenty-four hours it is removed, as has been stated, to the upper batter, where it is thoroughly dried in the course of three or four days. Before it is taken on board ship it is carefully picked, when the damp pieces are separated to return to the batter. It is stowed in bulk, and when fit for that purpose should be as hard and dry as chips. Great care must be taken to preserve it from moisture. In the process of drying it loses two-thirds both of its weight and bulk, and when cured resembles a smoked sausage. In this state it is sold by the picul, which brings from fifteen to twentyfive dollars.

Capt. Eagleston had collected, in the course of seven months, and at a trifling expense, a cargo of 1,200 piculs, worth about 25,000 dollars.

The outfit for such a voyage is small, but the risk incurred is of some moment, as no insurance can be effected on vessels bound to the Feejee group, and it requires no small activity and enterprise to conduct this trade. A thorough knowledge of the native character is essential to success, and it requires all possible vigilance on the part of the captain o the vessel to prevent surprise, and the greatest caution to avoid difficulties. Even with the exercise of these qualities he may often find himself and his crew in perilous positions. In order to lessen the danger as much as possible, no large canoes are ever allowed to remain alongside the vessel, and a chief of high rank is generally kept on board as a hostage. When these precautions have not been taken accidents have frequently happened.* -(Wilkes's Narrative of the United States' Exploring Expedition, vol. iii. pp. 218–223.)

In order to show the profits which arise from the trade in biche de mar, I give the cost and

VI.-ON CORAL REEFS.

BY CHARLES DARWIN, ESQ., F.R.S., &c.

An interesting paper on the coral reefs is given in the Geological Report of the United States' Exploring Expedition, by James D. Dana, Esq., the naturalist to the Expedition, It is also copied into the American Journal of Science (Silliman's) for May and July, 1851. In this treatise the numerous features of these singular structures are alluded to with great clearness, but it will be exceeding our space to give them here. The elaborate and standard work of Charles Darwin, Esq., on the same subject, embodies all that can be useful to the sailor, and we prefer giving this here, and for the purpose of brevity extract that gentleman's own remarks as given in the second edition of his valuable work.

Mr. Darwin says: --I will now give a very brief account of the three great classes of coral reefs: namely, Atolls, Barrier, and Fringing reefs, and will explain my views on their formation. Almost every voyager who has crossed the Pacific has expressed his unbounded astonishment at the lagoon islands, or as I shall for the future call them by their Indian name of Atolls, and has attempted some explanation. Even as long ago as the year 1605, Pyrard de Laval well exclaimed, "C'est une meruille de voir chacun de ces atollons, enuironné d'un grand banc de pierre tout autour, n'y ayant point d'artifice humain." The sketch of Whit Sunday Island in the Pacific, in Capt. Beechey's admirable voyage, gives but a faint idea of the singular aspect of an atoll: it is one of the smallest size, and has its narrow islets united together in a ring. The immensity of the ocean, the fury of the breakers, contrasted with the lowness of the land and the smoothness of the bright green water within the lagoon, can hardly be imagined without having been seen.

The earlier voyagers fancied that the coral building animals instinctively built up their great circles to afford themselves protection in the inner parts; but so far is this from the truth, that those massive kinds, to whose growth on the exposed outer shores the very existence of the reef depends, cannot live within the lagoon, where other delicately branching kinds flourish. Moreover, on this view, many species of distinct genera and families are supposed to combine for one end; and of such a combination, not a single instance can be found in the whole nature. The theory that has been most generally received is, that atolls are based on submarine craters; but when we consider the form and size of some, the number, proximity, and relative positions of others, this idea loses its plausible character: thus, Suadiva atoll is 44 geographical miles in diameter in one line, by 34 miles in another line; Rimsky is 54 by 20 miles across, and it has a strangely sinuous margin; Bow atoll is 30 miles long, and on an average only 6 miles in width; Menchicoff atoll consists of three atolls united or tied together. This theory, moreover, is totally inapplicable to the northern Maldiva atolls in the Indian Ocean (one of which is 88 miles in length, and between 10 and 20 miles in breadth), for they are not bounded, like ordinary atolls, by narrow reefs, but by a vast number of separate little atolls, other little atolls rising out of the great central lagoon like spaces. A third and better theory was advanced by Chamisso, who thought that the corals growing more vigorously where exposed to the open sea, as undoubtedly is the case, the outer edges would grow up from the general foundation before any other part, and that this would account for the ring or cup-shaped structure. But we shall immediately see

return of five cargoes, obtained by Capt. Eagleston in the Feejee group. These he obligingly favoured me with.

Fifth voyage

A further profit also arises from the investments of the proceeds in Canton. Capt. Eagleston also obtained 4,488 lbs. of tortoise-shell, at a cost of 5,700 dollars, which sold in the United States for 29,050 dollars net.

that in this, as well as in the crater theory, a most important consideration has been overlooked, namely, on what have the reef building corals, which cannot live at a great depth, based their massive structures.

Numerous soundings were carefully taken by Capt. FitzRoy on the steep outside of Keeling atoll, and it was found that within 10 fathoms the prepared tallow at the bottom of the lead invariably came up marked with the impression of living corals, but as perfectly clean as if it had dropped on a carpet of turf; as the depth increased the impression became less numerous, but the adhering particles of sand more and more numerous, until at last it was evident that the bottom consisted of a smooth sandy layer; to carry on the analogy of the turf, the blades of grass grew thinner and thinner, till at last the soil was so sterile that nothing sprang from it. From these observations, confirmed by many others, it may be safely inferred that the utmost depth at which the corals can construct reefs is between 20 and 30 fathoms. Now there are enormous areas in the Pacific and Indian Oceans, in which every single island is of coral formation, and is raised only to that height to which the waves can throw up fragments, and the winds pile up sand. Thus the Radack group of atolls is an irregular square 520 miles long by 240 miles broad; the Low Archipelago is elliptic formed, 840 miles in its longer and 420 miles in its shorter axis: there are other small groups and single low islands between these two archipelagos, making a linear space of ocean actually more than 4,000 miles in length, in which not one single island rises above the specified height. Again, in the Indian Ocean there is a space of ocean 1,500 miles in length, including three archipelagos, in which every island is low and of coral formation. From the fact of the reef-building corals not living at great depths, it is absolutely certain that throughout these vast areas, wherever there is now an atoll, a foundation must have originally existed within a depth of from 20 to 30 fathoms from the surface. It is improbable in the highest degree that broad, lofty, isolated, steep-sided banks of sediment, arranged in groups and lines hundreds of leagues in length, could have been deposited in the central and profoundest parts of the Pacific and Indian Oceans at an immense distance from any continent, and where the water is quite limpid. It is equally improbable that the elevatory forces should have uplifted, throughout the above vast areas, innumerable great rocky banks within 20 to 30 fathoms, or 120 to 180 feet of the surface of the sea, and not one single point above that level; for where, on the whole face of the globe, can we find a single chain of mountain, even a few hundred miles in length, with their many summits rising within a few feet of a given level, and not one pinnacle above it? If, then, the foundations, whence the atollbuilding corals spring, were not formed of sediment, and if they were not lifted up to the required level, they must of necessity have subsided into it; and this at once solves the difficulty. For as mountain after mountain, and island after island, slowly sank beneath the water, fresh bases would be successively afforded for the growth of the corals. It is impossible here to enter into all the necessary details, but I venture to defy any one to explain in any other manner how it is possible that numerous islands should be distributed throughout vast areas, all the islands being low, all being built of coral, absolutely requiring a foundation within a limited depth from the surface.

Before explaining how atoll reefs acquire their perpendicular structure, we must turn to the second great class, namely, Barrier reefs. These either extend in straight lines in front of the shores of a continent or of a large island, or they encircle smaller islands; in both cases being separated from the land by a broad and rather deep channel of water, analogous to the lagoon within an atoll. It is remarkable how little attention has been paid to encircling barrier reefs, yet they are truly wonderful structures. The sketch represents part of the barrier encircling the Island of Bola-Bola in the Pacific, as seen from one of the centre peaks. In this instance the whole line of reef has been converted into land; but usually a snow-white line of great breakers, with only here and there a single low islet crowned with cocoa-nut trees, divides the dark heaving waters of the ocean from the light green expanse of the lagoon channel. And the quiet waters of this channel generally bathe a fringe of low