thousands of years to come. As this is a matter of fact abfolutely indifputable, it is alfo a very obvious yet folid demonftration, that the principles of fcience, on which thofe calculations proceed, are not merely conjecture, or precarious fuppofition, but have a real, a certain foundation in the nature and conftitution of things." How vaft His power, that launch'd thofe fhining orbs CRIRIE. No. 3. COMETS.-Comets are defined to be folid compact bodies, like other planets, and regulated by the fame laws of gravity. They move about the fun in very eccentric orbits, and are of a much greater density than our earth; for fome of them are heated, in every period, to fuch a degree as would vitrify or diffipate any fubftance known to us. Comets are always attended with long tranfparent trains, or tails, iffuing from that fide of them which is turned away from the fun : that which appeared in 1680 drew after it a tail of fire that was computed to be 80,000,000 miles in length. The ufe of the comet's huge vapoury train" is 66 -perhaps to fhake Reviving moisture on the numerous orbs To light up worlds, and feed the eternal fire. THOMSON. There are fuppofed to be a confiderable number of comets belonging to the folar fyftem; but the periods of three of them only are known with any certainty*. Thefe return at intervals of 75, 129, and 575 years. Dr. Halley, at first, fuppofed the comets of 1532 and 1661, to be one and the fame; and though he afterwards feemed to retract this opinion, it has been generally adopted by aftronomers. They accordingly expected its return, making an allowance for its retardation, in 1789. Agreeably to this conjecture, Dr. Maskelyne had calculated that it ight be certainly expected before the 27th of April in that year. In this inftance, however, the expectation of aftronomers has been difappointed; and it remains for future obfervation to afcertain the periodical return of this eccentric planet. The comet which appeared in 1680, travelled, when neareft to the fun, with the amazing velocity of 880,000,000 of miles in an hour. Its greatest distance from the fun is computed at 11,200,000,000 of miles, and its least distance at 490,00o, at which time it is faid to be 2000 times hotter than red hot iron.. This comet approaches, in one part of its orbit, very nearly to the orbit of our earth; fo that, according to fome eminent philofophers, it may, in fome future revolutions, approach near enough to have very confiderable, if not fatal effects upon it. See Exer. on the Globes, 4th edit. art. Comets. No. 4. FIXED STARS.-Thefe are fo called, becaufe they always maintain the fame pofition, or relative dif tance from each other; their apparent diurnal motion being caufed folely by the earth's turning on its axis. The fixed ftars are fuppofed to be fo many funs equal in dimenfions to our fun, and each star is held to be the centre of a system, and to have planets or earths revolving round it, in the fame manner as our fun; or, in other words, that many opaque bodies are illuminated, warmed, and cherished by its light: * It is mortifying, fays the late famous French afronomer La Lande, that, at prefent, we know not whether we are to reckon, comets by hundreds or by thousands ;-whether they return, or are loft in the immenfity of the universe. Confult Confult with reafon, reafon will reply, And fills, with glory, its appointed place: Mathematicians affert, that Sirius*, or the Dog Star, is the nearest to us of all the fixed ones; and they compute its diftance from our earth at 2,200,000,000,000 of miles. They maintain that a found would not reach our earth from Sirius in 50,000 years; and that a cannon-ball, flying with its ufual velocity, of 480 miles an hour, would confume 523,211 years in its paffage thence to our globe. No. 5. OF THE INVENTION OF ALPHABETICAL LETTERS, AND THE ART OF WRITING.-Writing is the art of conveying our ideas to others by letters, or characters vifible to the eye. To whom we are indebted for this admirable and useful difcovery, does not appear. Many learned men have fuppofed, that the alphabet was of divine origin; and feveral writers have afferted, that letters were first communicated to Mofes by God himself ; whilft others have contended, that the decalogue was the first alphabetical writing. Again, many authors have decided in favour of the ancient inhabitants of Egypt: "There firft the marble learn'd to mimic life, "His radiant way, and heavens were taught to roll." Others have maintained the claim of the Phoenicians to the invention of letters : Phoenicians firft, if ancient fame be true, * See Exercises on the Globes, 4th edition. The The power of words by figures rude convey'd, Rowe's Lucan's Pharfalia, The Chaldeans have alfo had feveral learned advocates, who have attributed the invention of letters to the patriarch Abraham; and Sir Ifaac Newton, in particular, admits that letters were known in the Abrahamic time for fome centuries before Moses. Mr. Gilbert Wakefield was one of thofe learned writers, who maintained, that the art of alphabetical writing appears to be of divine origin: in his ingenious Effay on this fubject, he obferves, that the Phoenicians, and their colonists the Carthaginians, fpoke the Hebrew language, or a dialect fcarcely varying from the original; and that all the languages in ufe among men, which have been conveyed in alphabetical characters, were the languages of people connected ultimately, or immediately, with those who have handed down the earliest specimens of writing to pofterity, viz. the authors of the first five books of the Old Teftament; which are acknowledged by all to be, not only the most ancient compofitions, but alfo the most early fpecimens of alphabetical writing, at prefent exifting in the world. to Mr. More, in his Effay upon the Invention of Writing, informs us, that the various combinations of the 24 letters, and none of them repeated twice, will amount 620,448,401,733,239,439,360,000. But Clavius, the Jefuit, who alfo computed thefe combinations, makes the numbers to be but 5,852,616,738,497,664,000. No. 6. DIFFICULTY OF APPREHENDING HIGH NUMBERS. AS very high numbers are fomewhat difficult to apprehend, we naturally fall on contrivances to fix them in our minds, and render them familiar: but notwithstanding all the expedients that we can contrive, our ideas of high numbers are ftill imperfect, and generally far fhort of the reality; and though we can perform any computation with exactnefs, the anfwer that we obtain is often incompletely apprehended. It may not be amifs to illuftrate, by a few examples, the extent of numbers which are frequently named without being attended to. If a perfon employed in telling money reckon an hundred pieces in a minute, and continue at work ten hours each day, he will take nearly feventeen days to reckon 1,000,000; a thousand men would take 45 years to reckon 1,000,000,000,000. If we suppose the whole earth to be as well peopled as Great-Britain, and to have been fo from the creation, and that the whole race of mankind had conftantly fpent their time in telling a heap confifting of 1,000,000,000,000,000,000,000,000 of pieces, they would hardly have yet reckoned a thoufandth part of that quantity. Ency. Brit. art. Arithmetic. TEAC ADDITION EACHES to add feveral fums together into one whole, or total. EXAMPLE S. No. 7. CREATION OF THE WORLD. Man, as the pious. Hervey remarks, being greatly beloved by his Creator, is conftituted master of this globe. The fields are his exhauftlefs granary: the ocean his vaft reservoir. The animals fpend their ftrength to dispatch his bufinefs; refign their clothing to replenish his wardrobe; and furrender their very lives to provide for his table: Man, more divine, is master of all these, SHAKSPEARE. For him kind nature wakes her genial pow'r, B 5 For |