CLEPSYDRE, OR WATER-CLOCKS. BEFORE the invention of clocks, the only instruments used for the measurement of time were the sun-dial and the water-clock; the sun-dial could only be employed in the day-time, but the waterclock supplied its place during the night. The invention of both these instruments is attributed to the Egyptians; the sun-dial is supposed to have been the first invented. The peculiar method in which this ancient people divided their time into twelve hours, from sunrise to sunset, and twelve hours from sunset to sunrise, rendered the construction of an accurate clepsydra a matter of some difficulty, since it was necessary that the instrument should each day, according to the season of the year, indicate hours of a different length. The modern method of dividing the day and night into twenty-four equal portions, has removed much of the difficulty in the construction of a water-clock. Although the invention of clocks and watches has thrown these instruments into disuse, they might still be made effective measurers of time, if the resources of modern science were directed to their improvement.

In noticing several of these curious instruments, we shall confine ourselves to the description of those whose construction is most simple, and least likely to give an incorrect result; the simplest mode of measuring time by the means of water, is the following. Let a glass vessel A, say twelve or fourteen

The ingenuity displayed in the invention of this water-clock, is confined to the construction of the cylindrical box which acts as the weight; it is clear that if this box acted simply as a weight, and was equally heavy all round its axis, it would very quickly reach the stand of the instrument, and the twelve hours would be told in perhaps twelve seconds. If one side of the box was made heavier than the other, as soon as that part was undermost, it must come to a stand-still, as the lighter portion would never be able to roll it over.

inches in length, be suspended in an iron frame, Fig. 3 shows the internal construction of this attached to a tin vessel B; at the bottom of the glass rolling-weight, the white vessel at c is a small hole, through which water, if spaces tending to the cenplaced in the vessel itself, will gradually fall in drops; tre represent so many dithe size of this hole must be so managed, as to cause visions of thin metal; a the vessel to be emptied in rather more than twelve certain quantity of water hours: the descent of the surface of the water in the is introduced into this glass vessel will point out the time that has elapsed divided box, and it will, since it was filled, and, consequently, indicates the in the first instance, astime of day; but as, when the vessel is full, the water sume the situation marked escapes more rapidly than afterwards, the interval in the engraving, or somebetween the first and second hour will be longer than thing like it; the natural that between the second and third, and this last than consequence of this will that between the third and fourth, and so on. The be, that the cylinder will have a tendency towards the relative distances of each of the hour-marks may be left in its descent; the altered position of the cylinder marked on the side of the glass, by noting the place will, at the same time, have altered the relative situaoccupied by the surface of the water during twelve tions of the different quantities of water, and as the successive hours, taking the time from a well-regu- divisions do not quite reach the circumference of the lated clock. The same end may be attained by cal-cylinder, the quantity contained in each division will be culation, but to render the method intelligible would require too much space.

The second engraving represents a water-clock of rather higher pretensions as a work of art; in this case the hours are indicated on a dial in the same manner as in many turret-clocks by a single hand. This hand is moved round at a uniform rate by the revolution of the cylindrical box; in its descent the

also changed, and the greatest weight will be on the right-hand side; by this alternate action, the descent of the weight is retarded, the water acting something after the manner of the pendulum of a clock.

The third engraving represents a more complicated, but extremely ingenious, clepsydra. The water by which the machine is kept in motion is contained in the reservoir at H, from this it descends by the pipe A,

has been discovered, each animalcule being provided with appropriate organs, endowed with spontaneous powers of motion, and giving unequivocal signs of individual vitality.

Thus, if we review every region of the globe, from the scorching sands of the equator to the icy realms of the poles, or from the lofty mountain-summits to the dark abysses of the deep; if we penetrate into the shades of the forest, or into the caverns and secret recesses of the earth; nay, if we take up the minutest portion of stagnant water, we still meet with life in some new and unexpected form, yet ever adapted to the circumstances of its situation. Wherever life can be sustained, we find life produced. It would almost seem as if Nature had been thus lavish and sportive in her productions, with the intent to demonstrate to man the fertility of her resources, and the inexhaustible fund from which she has so prodigally drawn forth the means requisite for the maintenance of all these diversified combinations, for their repetition in endless perpetuity, and for their subordination to one harmonious scheme of general good. The vegetable world is no less prolific in wonders than the animal. In this, as in all other parts of creation, ample scope is found for the exercise of the reasoning faculties, and abundant sources are supplied of intellectual enjoyment. To discriminate the different characters of plants, amidst the infinite diversity of shape, of colour, and of structure, which they offer to our observation, is the laborious, yet fascinating, occupation of the botanist. Here, also, we are lost in admiration at the never-ending variety of forms successively displayed to view in the innumerable species which compose this kingdom of nature, and at the energy of that vegetative power, which, amidst such great differences of situation, sustains the modified life of each individual plant, and which continues its species in endless perpetuity. Wherever circumstances are compatible with vegetable existence, we there find plants arise. It is well known that, in all places where vegetation has been established, the germs are so intermingled with the soil, that whenever the earth is turned up, even from considerable depths, and exposed to the air, plants are soon observed to spring, as if they had been recently sown, in consequence of the germination of seeds which had remained latent and inactive during the lapse of perhaps many centuries. Islands formed by coral-reefs, which have risen above the level of the sea, become, in a short time, covered with verdure. From the materials of the most sterile rock, and even from the yet recent cinders and lava of the volcano, Nature prepares the way for vegetable existence. The slightest crevice or inequality is sufficient to arrest the invisible germs that are always floating in the air, and affords the means of sustenance to diminutive races of lichens and mosses. These soon overspread the surface, and are followed, in the course of a few years, by successive tribes of plants of gradually-increasing size and strength; till at length the island, or other favoured spot, is converted into a natural and luxuriant garden, of which the productions, rising from grasses to shrubs and trees, present all the varieties of the fertile meadow, the tangled thicket, and the widely-spreading forest. Even in the desert plains of the torrid zone, the eye of the traveller is often refreshed by the appearance of a few hardy plants, which find sufficient materials for their growth in these arid regions: and in the realms of perpetual snow which surround the poles, the navigator is occasionally startled at the prospect of fields of a scarlet hue, the result of a wide expanse of microscopic vegetation.

[ROGET'S Bridgewater Treatise.]

THE MAIN-TRUCK, OR, A LEAP FOR LIFE.

Stand still! How fearful

And dizzy 'us to cast one's eyes so low!........
.The murmuring surge,

That on th' unnumber'd idle pebbles chafes,
Cannot be heard so high :-I'll look no more;
Lest my brain turn, and the deficient sight
Topple down headlong.-SHAKSPEARE.
AMONG the many agreeable associates whom my different
eruisings and wanderings have brought me acquainted
with, I can scarcely call to mind a more pleasant and
companionable one than Tom Scupper. Poor fellow! he
is dead and gone now-a victim to that code of false
honour which has robbed the navy of too many of its
short and delightful cruise, and, a good part of the time,
choicest officers. Tom and I were messmates during a
we belonged to the same watch. He was a great hand to.
spin yarns, which, to do him justice, he sometimes did
tolerably well; and many a long mid-watch has his fund
of anecdote and sea-stories caused to slip pleasantly away.
We were lying in the open roadstead of Laguayra, at single
relate, as nearly as I can remember, in his own words. A
anchor, when Tom told me the story which I am about to
vessel from Baltimore had come into Laguayra that day,
and by her I had received letters from home, in one of
which there was a piece of intelligence that weighed
heavily on my spirits. For some minutes after our watch
commenced, Tom and I walked the deck in silence, which
was soon, however, interrupted by my talkative companion,
thoughts, told me the story which I am now about to relate,
who, perceiving my depression, and wishing to divert my
for the entertainment of the reader.

The last cruise I made in the Mediterranean, said he, was in old Ironsides, as we used to call our gallant frigate. We had been backing and filling for several months on Messurado, in search of slave-traders; and during that the western coast of Africa, from the Canaries down to time we had had some pretty heavy weather. When we reached the Straits, there was a spanking wind blowing from about west-south-west; so we squared away, and, without coming-to at the Rock, made a straight wake for old Mahon, the general rendezvous and place of refitting arriving there, we warped in alongside the Arsenal quay, for our squadrons, in the Mediterranean. Immediately on tiers, and store-rooms, and gave her a regular-built overwhere we stripped ship to a girtline, broke out the holds, hauling from stem to stern. For a while, every body was busy, and all seemed bustle and confusion. Orders and replies, in loud and dissimilar voices, the shrill pipings of the different boatswains' mates, each attending to separate duties, and the mingled clatter and noise of various kinds of work, all going on at the same time, gave something of the stir and animation of a dock-yard, to the usually quiet arsenal of Mahon. The boatswain and his crew were engaged in fitting a new gang of rigging; the gunner in repairing his breechings and gun-tackles; the fo castle-men in calking; the top-men in sending down the yards and upper spars; the holders and waisters in whitewashing and like beasts of burden, in carrying breakers of water on holy-stoning; and even the poor marines were kept busy, their backs. On the quay, near the ship, the smoke of the armourer's forge, which had been hoisted out, and sent ashore, ascended in a thin column through the clear blue sky; from one of the neighbouring white stone warehouses, the sound of saw and hammer told that the carpenters the cooper, who, in the open air, was tightening the waterwere at work; near by, a livelier rattling drew attention to casks; and not far removed, under a temporary shed, formed of spare studding-sails and tarpaulins, sat the sail-maker and his assistants, repairing the sails, which had been rent or injured by the many storms we had encountered.

Many hands made light work, and in a very few days all was accomplished: the stays and shrouds were set up, and new rattled down, the yards crossed, the running rigging rove, and sails bent; and the old craft, fresh painted and all a-taunt-o, looked as fine as a midshipman on liberty. In place of the storm-stumps, which had been stowed away among the booms, and other spare spars, amidships, we had sent up cap to`gallant-masts, and royal poles, with a sheave for skysails, and hoist enough for sky-scrapers above them: There was a Dutch line-ship in the harbour; but though so you may judge the old frigate looked pretty taunt. we only carried forty-four to her eighty, her main-truck would hardly have reached to our royal-mast-head. The

side-boys, whose duty it was to lay aloft, and furl the sky- ning back at the negro, as if there existed some means of sails, looked no bigger on the yard than a good-sized duff mutual intelligence between them. It was my watch on for a midshipman's mess, and the main-truck seemed not-deck, and I stood awhile leaning on the main fife-rail and half as large as the Turk's-head-knot on the man-ropes of amusing myself by observing the antics of the black and the accommodation-ladder. his congenial playmate; but at length, tiring of the rude mirth, I walked towards the taffrel, to gaze on the more agreeable features of the scene I have attempted to describe. Just at that moment a shout and a merry laugh burst upon my ear, and looking quickly round to ascertain the cause of the unusual sound on a frigate's deck, I saw little Bob Stay (as we called our commodore's son) standing half-way up the main-hatch ladder, clapping his hands, and looking aloft at some object which seemed to inspire him with a deal of glee. A single glance to the main-yard informed me of the occasion of his merriment. He had been coming up from the gun-deck, when Jacko, perceiving him on the ladder, dropped suddenly down from the main-stay, and running along the boom-cover leaped upon Bob's shoulder, seized his cap from his head, and immediately darted up the main-topsail-sheet, and thence to the bunt of the mainyard, where he now sat, picking threads from the tassel of his prize, and occasionally scratching his side, and chattering, as if with exultation at the success of his mischief. But Bob was a sprightly, active little fellow; and though he could not climb quite as nimbly as a monkey, yet he had no mind to lose his cap without an effort to regain it. Perhaps he was the more strongly incited to make chase after Jacko, by seeing me smile at his plight, or by the loud laugh of Jake, who seemed inexpressibly delighted at the occurrence, and endeavoured to evince, by tumbling about the boom-cloth, shaking his huge misshapen head, and sundry other grotesque actions, the pleasure for which he had no words

When we had got every thing ship-shape, aud man-ofwar fashion, we hauled out again, and took our berth about half-way between the arsenal and Hospital Island; and a pleasant view it gave us of the town and harbour of old Mahon, one of the safest and most tranquil places of anchorage in the world. The water of this beautiful inlet, which, though it makes about four miles into the land, is not much over a quarter of a mile in width,-is scarcely ever ruffled by a storm; and on the delightful afternoon to which I now refer, it lay as still and motionless as a polished mirror, except when broken into momentary ripples, by the paddles of some passing waterman. What little wind there had been in the fore-part of the day, died away at noon, and, though the first dog-watch was almost out, and the sun near the horizon. not a breath of air had risen to disturb the deep serenity of the scene. The Dutch liner, which lay not far from us, was so clearly reflected in the glassy surface of the water, that there was not a rope about her, from her main-stay to her signal halliards, which the eye could not distinctly trace in her shadowy and inverted image. The buoy of our best bower floated abreast our larboard bow; and that, too, was so strongly imaged, that its entire bulk seemed to lie above the water, just resting on it, as if upborne on a sea of molten lead; except when now and then, the wringing of a swab, or the dashing of a bucket overboard from the head, broke up the shadow for a moment, and showed the substance but half its former apparent size. A small polacca craft had got under-way from Mahon in the course of the forenoon, intending to stand over to Barcelona; but it fell dead calm just before she reached the chops of the harbour; and there she lay as motionless upon the blue surface, as if she were only part of a mimic scene, from the pencil of some accomplished painter. Her broad cotton lateen sails, as they hung drooping from the slanting and taper yards, shone with a glistening whiteness that contrasted beautifully with the dark flood in which they were reflected; and the distant sound of the guitar, which one of the sailors was listlessly playing on her deck, came sweetly over the water, and harmonized well with the quiet appearance of every thing around. The whitewashed walls of the lazaretto, on a verdant headland at the mouth of the bay, glittered like silver in the slant rays of the sun; and some of its windows were burnished so brightly by the level beams, that it seemed as if the whole interior of the edifice were in flames. On the opposite side, the romantic and picturesque ruins of fort St. Philip, faintly seen, acquired double beauty, from being tipped with the declining light; and the clusters of ancient-looking windmills, which dot the green eminences along the bank, added, by the motionless state of their wings, to the effect of the unbroken tranquillity.

Even on board our vessel, a degree of stillness unusual for a man-of-war, prevailed among the crew. It was the hour of their evening meal; and the low murmur from the gun-deck had an indistinct and buzzing sound, which, like the dreamy hum of bees on a warm summer-noon, rather heightened, than diminished the charm of the surrounding quiet. The spar-deck was almost deserted. The quartermaster of the watch, with his spy-glass in his hand, and dressed in a frock and trowsers of snowy whiteness, stood aft upon the taffel, erect and motionless as a statue, keeping the usual look-out. A group of some half-dozen sailors had gathered together on the fo castle, where they were supinely lying under the shade of the bulwarks; and here and there, upon the gun-slides along the gangway, sat three or four others,-one, with his clothes-bag beside him, overhauling his simple wardrobe; another working a set of clues for some favourite officer's hammock; and a third engaged, perhaps, in carving his name in rude letters upon the handle of a jack-knife, or in knotting a laniard, with which to suspend it round his neck.

On the top of the boom-cover, in the full glare of the level sun, lay black Jake, the jig-maker of the ship, and a striking specimen of African peculiarities, in whose single person they were all strongly developed. His flat nose was dilated to unusual width, and his ebony cheeks fairly glistened with delight, as he looked up at the gambols of a large monkey, which, clinging to the main-stay, just above Jake's woolly head, was chattering and grin

66

Ha, you rascal Jocko, hab you no more respec' for de young officer, den to steal his cab? We bring you to de gangway, you black nigger, and gib you a dozen on de bare back for a tief."

The monkey looked down from his perch as if he understood the threat of the negro, and chattered a sort of deflance in answer.

66

Ha, ha! Massa Stay, he say you mus' ketch him 'fore you flog him; and it's no so easy for a midshipman in boots to ketch a monkey barefoot."

A red spot mounted to little Bob's cheek, as he cast one glance of offended pride at Jake, and then sprang across the deck to the Jacob's ladder. In an instant he was halfway up the rigging, running over the ratlines as lightly as if they were an easy flight of stairs, whilst the shrouds scarcely quivered beneath his elastic motion. In a second more his hand was on the futtocks.

"Massa Stay," cried Jake, who sometimes, being a favourite, ventured to take liberties with the younger officers; Massa Stay, you best crawl through de lubber's hole-it take a sailor to climb de futtock shroud."

But he had scarcely time to utter his pretended caution, before Bob was in the top. The monkey, in the mean while, had awaited his approach, until he got nearly up the rigging, when it suddenly put the cap on its own head, and running along the yard to the opposite side of the top, sprang up a rope, and thence to the topmast backstay, up which it ran to the topmast cross-trees, where it again quietly seated itself, and resumed its work of picking the tassel to pieces. For several minutes I stood watching my little messmate follow Jacko from one piece of rigging to another, the monkey, all the while, seeming to exert only so much agility as was necessary to elude the pursuer, and pausing whenever the latter appeared to be growing weary of the chase. At last, by this kind of manoeuvring, the mischievous animal succeeded in enticing Bob as high as the royal-mast-head, when, springing suddenly on the royal stay, it ran nimbly down to the fore-to-gallant-mast-head, thence down the rigging to the foretop, and leaping on the foreyard, it ran out to the yard-arm, hung the cap on the end of the studding-sail boom, and there taking its seat, it raised a loud and exulting chattering. Bob by this time was completely tired out, and, unwilling, perhaps, to return to the deck to be laughed at for his fruitless chase, sat down in the royal cross-trees, while those who had been attracted by the sport, returned to their usual avocations or amusements. The monkey, no longer the object of pursuit or attention, remained but a little while on the yard-arm, but soon taking up the cap, returned in towards the slings, and dropped it down upon the deck.

Some little piece of duty occurred at this moment to