The ravages committed by this creature are almost incredible. Wood of every description is devoured by the Ship-worm, whose tunnels are frequently placed so closely together that the partition between them is not thicker than the paper on which this account is printed. As the Teredo bores, it lines the tunnel with a thin shell of calcareous matter, thus presenting a remarkable resemblance to the habits of the white ant. When the Teredos have taken entire possession of a piece of timber, they destroy it so completely that, if the shelly lining were removed from the wood, and each weighed separately, the mineral substance would equal the vegetable in weight.

The Ship-worm has been the cause of numerous wrecks, for it silently and unsuspectedly reduces the plankings and timbers to such a state of fragility that, when struck by the side of a vessel, or even by an ordinary boat, large fragments will be broken off. I have now before me two specimens of "worm-eaten" timber, one of which is so honey-combed by this destructive mollusk, that a rough grasp of the hand would easily crush it. Yet this fragment formed part of a pier on which might have depended a hundred lives, and which was so stealthily sapped by the submarine miners, that its unsound state was only discovered by an accident.

The copper sheathing, with which the bottoms of ships are covered, is placed upon them for the express purpose of baffling the Ship-worm, and, though so expensive a process, is cheaper than permitting the destructive creature to work its own will on the vessel. It is possible, however, that an equally effectual, and very much cheaper method of protecting ships and submerged timber may soon be brought into active operation. M. de Quatrefages has discovered that mercurial salts of any kind are instantaneously fatal to the Ship-worm, and that, by their use, not only the existing animals may be killed, but their eggs destroyed also. A vessel that has been attacked by these pests may be rid of them by throwing a few pounds of corrosive sublimate into the dock where she lies, and it would not be very difficult to keep a special dock for the purpose.

The most effectual method, however, of checking the ravages of the Ship-worm is, by saturating the timber with corrosive sublimate; a process which is effected by exposing the timber for a long period of time, so as to allow the sap to escape, and then by forcing a solution of the metallic poison into the minute inter

stices of the wood. This is done in a curiously simple manner, namely, by laying the logs of timber on the ground, introducing a tube into one end, carrying the tube to a height of forty or fifty feet, and then connecting it with a tank filled with the solution. It is, of course, necessary that the timber should be thoroughly seasoned before it is thus treated. M. de Quatrefages suggests that the prepared wood might be sawn into thin planks, which could then be used in the same manner as the copper sheathing

now in use.

Another species of the same genus, Teredo corniformis, is remarkable for the locality in which it is found. This curious mollusk burrows into the husks of cocoa-nuts and other thick woody fruits which may be found floating in the tropical seas. In consequence of the locality which it selects for its habitation, it can not proceed in one direction for any great distance, and is obliged to make its burrows in a crooked form, which has earned for the creature the specific title of corniformis, or horn-shaped. Fossil woods are often found perforated with these burrows.

Destructive as it may be, the Ship-worm will ever be an object of interest to Englishmen, inasmuch as its shell-lined burrow gave to Sir I. Brunel the idea which was afterward so efficiently carried out in the Thames Tunnel. And though, from the alteration of surrounding circumstances, that wonderful monument of engineering skill has not been so practically useful as was anticipated, it has proved of incalculable value as pioneer to the numerous railway tunnels of this and other countries.

The largest species of this curious genus is the GIANT TEREDO (Teredo gigantea), which produces a shell more than five feet in length and three inches in diameter. The substance of the shell is of very great strength, being about half an inch in thickness, radiated in structure, and so hard that when the first specimen was brought to England many naturalists took it for a hollow stalactite.

This creature is a burrower into mud, and was discovered in a very curious manner. In the year 1797, a violent shock of earthquake took place in Sumatra, and caused great upheavals of earth and corresponding floods of water. When the sea receded from one of the bays, certain unknown objects were seen protruding from its muddy bed, and were pulled out with tolerable ease. They projected about eight or ten inches from the mud, and as the projecting portions were beset by serpulæ, bi

valves, and other marine parasites, it was evident that they were not forced out of the mud by the shock, but had been in that position for a considerable time. All, however, were damaged, one or both ends being broken off. Their color was pure white on the exterior, and yellowish within. None of them were perfectly straight, and the greater number more or less contorted.

CHAPTER VI.

BURROWING SPIDERS.

The SCORPION and its Habits.-The Burrow of the Scorpion.-How detected.— Suicide among the Scorpions.-Spiders and their Burrows.-The Atypus.—Madame Merian and her Book of the BIRD SPIDER.-Mr. Bates's Discoveries.-Hair of the Bird Spider.-The TARANTULA.-Its Ferocity and Courage.—The TRAPDOOR SPIDER.-Its Tunnel and the Lining thereof.-Its Appearance under the Microscope. The "Trap-door" itself, and its Structure.-Curious Example of Instinct.-Activity of the Spider.-Specimen in the British Museum.-Strength and Obstinacy of the Trap-door Spider.-An Australian Trap-door Spider.

AMONG the burrowers belonging to this order may be reckoned the well-known SCORPION, of which there are several species, resembling each other in their general appearance, their structure, and their habits.

Scorpions are found in all the warmer portions of the globe, and under the tropics they may be said to swarm. They are, as a general rule, intolerant of light, creeping by day into every cranny that can shelter them from the unwelcome sunbeams, and often causing very great annoyance by this custom. Old travelers, who have learned by experience the habits of these creatures, do not retire to rest before they have carefully examined the bed and surrounding furniture, especially taking up the pillow, and seeing that no enemy has lodged within the folds of the bedding. The left hand is generally employed in lifting the clothes, while the right is armed with a boot-jack, or stout shoe, or some other convenient weapon, with which the Scorpion may be immolated to the just wrath of its discoverer, before it can run off and hide itself afresh. Shoes, boots, and gloves are also favorite resorts of the Scorpion, which has caused many an inexperienced traveler to buy future caution at rather a dear rate.

Scorpions may be found every where, under every stone, and in every crevice; and it not unfrequently happens that when a

pedestrian is passing over a sandy bank, and happens to break away a portion of it with his feet, a great black scorpion comes tumbling down, rolling over and over among the sandy avalanche, disengaging itself with an angry snap of its claws and a savage whisk of its tail, and showing fight as if it expected immediate attack from some present enemy. In such cases, the Scorpion has been a true burrower, excavating a temporary dwelling in the sandy soil, and living therein during the day.

The burrows of the Scorpion can always be detected by the peculiar shape of the entrance, which is of a semilunar form, exactly fitting the outline of the animal which digs it. The shape of the aperture is not unlike that of the hole which is cut in the seats of wooden stools for the purpose of introducing the hand when they are lifted. Wherever the soil is suitable for their purpose, the Scorpions take every advantage of it, so that a great number of these venomous creatures may be found in a comparatively small space of ground. Captain Pasley, R.A., tells me that, while in India, he has often destroyed, in the space of an hour or so, more than forty Scorpions, which had dug their sandy burrows in his garden.

The semilunar shape of the entrance is an infallible indication of the inhabitant, and in order to find out whether the Scorpion is at home, a jug full of water is poured into the burrow. Scorpions detest water, and when they feel the stream pouring upon them, they issue from their holes in high dudgeon, their pincers preceding them and snapping wildly at the enemy. A fork or spade is then driven under the Scorpion, and its retreat being thus cut off, it is easily killed.

The same officer also mentioned, that he had repeatedly tried the experiment of surrounding the Scorpion with a ring of fire, and that it had invariably stung itself to death. The fiery circle was about fifteen inches in diameter, and composed of smouldering ashes. In every instance the Scorpion ran about for some minutes, trying to escape, and then deliberately bent its tail over its back, inserted the point of its sting between two of the segments of the body and speedily died. This experiment was repeated seven or eight times, and always with the same results, so that a farther repetition would have been but a useless cruelty. The heat given out by the ashes was very trifling, and not equal to that which is caused by the noontide sun, a temperature which the Scorpion certainly does not like, but which it can endure

I

without suffering much inconvenience. Generally, the Scorpion was dead in a few minutes after the wound was inflicted.

MANY of the true spiders are among the burrowers, and, even in our own country, it is possible to see a sandy bank studded with their silk-lined tunnels.

There is such a bank that skirts a fir-wood near my house, the material being the loosest possible sandstone, scarcely hard enough in any place to resist a pinch between the fingers and thumb. About an inch or two above the soil, this sandstone is quite excavated by the spiders, and as the sandy sides of their tunnels would fall in were they not supported in some manner, every tunnel accordingly is lined by a coating of tough webbing, very strong, very elastic, very porous, and yet not suffering one particle of sand to pass through its interstices. From the opening of each burrow a web is spread, looking very much like a casting-net, with a hole through its middle. From this, again, radiate a number of separate threads, which extend to a considerable distance from the entrance.

At the very bottom of its silken tunnel the living architect. lies concealed, its sensitive feet resting on the web, so that it is enabled to perceive the approach of the smallest insect that crosses the spot which it has so elaborately fortified. It is curious to watch the various insects that are caught by different species of spiders. The common garden spider (Epeira diadema) enjoys the greatest variety of diet, and the water spider, of which we shall see something in a future page, is also capable of varying its food to a considerable extent. The Burrowing Spiders, however, of which there are several species, are much restricted in their diet, the chief food that is found in their webs consisting of small beetles and midges. These spiders belong to the family Agelenidæ.

ONE of the best, if not indeed the very best, examples of the British burrowing Arachnida is the remarkable species Atypus Sulzeri, a creature which is so rare as to have received no English name. It is a small species, not half an inch in length, but it is a curiously-constructed being; and were it made on a larger scale, would be a really formidable species. Its jaws are long, sharply pointed, and remarkably stout at their bases-so stout, indeed, that, but for a remarkable adaptation of structure, it would not be able to see any thing in front.