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uamnu Mart Imbrium, to be as fertile as the Campania. SessJSdin. Phil. Jour. iVb. SI, for July, 1824. Similar remarks to those now stated will apply to these conjectures of Schroeter. We are too apt to imagine, that ihe objects we perceive in the moon must bear a certain resemblance to those with which we are acquainted on the earth; whereas, there is every reason to believe, from the variety we perceive in nature, that no one world resembles another, except in some of its more prominent and general arrangements. The moon bears a general resemblance to the earth, in its being diversified with mountains and valleys; but the positions and arrangement of these objects in the moon, and the scenery they exhibit, are materially different from what appears on the surface of the terraqueous globe.

No. V.—On the ideas of Magnitude, Motion, and Duration, as exprtssed by number*. See pp. 44, 46.

In the pages referred to, and other parts of this volume, some very large numbers are expressed in JSgures. Some readers have insinuated, that it would have been better to have expressed such numbers in word*. The author, however, is of a different opinion ; because to some readers, not much acquainted with name* ration, a thousand trillions would convey nearly the same idea as a thousand nomltons, though the one number contains 68 places of figures, and the other only 22. It is chiefly the number of figures, or ciphers, in such large sums, that leads us to form a comparative estimate of their value or extent. Our ideas of magnitude and extension, conveyed by such numbers, must, of course, be very vague and undefined. If we have been accustomed to travelling, we have a tolerable clear conception of a hundred, and even of a thousand miles; but we have no clear nor adequate conception of a body, or a portion of space, ten hundred thousand, ten hundred millions, or ten hundred billions of miles in extent. The mind, however, may be assisted in its conceptions, and in its comparative estimate of different numbers, by fixing on some particular number as a standard. If, according to the common reckoning, we suppose, that 5838 years have elnpsed since the commencement of time, the number of seconds, or moments, in this period, will amount to 183,913,782,212, or one hundred and eightythree thousand nine hundred and thirteen millions, seven hundred and eighty-two thousand, two hundred and twelve, which is less than the fifth part of a billion. If the distance of the nearest stars from the earth be at least 20 billions of mites, then this distance may be otherwise expressed, by saying, that the number of miles which intervene between us and I hose bodies is more than a hundred timet greater than the number of moments which have elapsed since

the creation; and, by a similar comparison, ii will be found that the number of cubical miles within the iimits of the planetary system, is 130,000,000,000,000,000, or one hundred and thirty thousand billions of times greater than the number of moments in 5828 years.

It has been computed, that the earth, supposing it a solid globe, contains about 30,000,000,000,000,000,000,000,000,000,000, or thirty sentillions of grains of sand, supposing a hundred grains of sand to be equal in length to an inch, and, consequently, a million of such grains for every cubical inch. If we use this number a* a standard for estimating the number of cubical miles contained within the space which intervenes between us and the nearest stars, '^afl find that the number of cubical miles comprehended within this space, is more than ten thousand millions of times greater than the number of the grains of sand contained in the globe on which we dwell.

Though the human mind can form no definite conceptions of such numbers and magnitudes, yet it may be useful, occasionally, to ruminate on such subjects; as it is the only, or, at least, the principal mode by which limited mind* like ours can approximate to an idea of the infinity of the Creator. And if an tmage of infinity is presented to the mind in the spaces comprehended within the limits of our system, how overpowering the conception of innumerable systems, to which ours bears no more proportion than a drop of water to the mighty ocean t How ineffably glorious must be the attributes of that incomprehensible Being who pervades every part of this vast universe, and who continually superintends all its minute and diversified movements'

No. VI. p. 91—On a Plurality of Worlds,

The doctrine of a plurality of worlds is now admitted as highly probable both by philosophers and by enlightened divines. But it has been admitted by many persons on grounds that are too general and vague, and consequently, a fuQ conviction of its truth is seldom produced in the mind. In different parts of the preceding volume, I have all along taken it for granted, because I consider it as susceptible of a moral demonstration. The following heads of argument, were they fully illustrated, would go far to carry demonstration to the mind on this subject: namely, That there are numerous bodies in the universe of a bulk sufficient to contain myriads of intelligent beings, and to afford them enjoyment—tha* there appears, in the constitution of many of these bodies, a variety of arrangements evidently adapted to this end—that, in relation te the planets of our system, there are many circumstances which bear a striking resemblance to the constitution of our globe and its appenoagce-. they have annual uad diurnal motions, moons, atmospheres, mountains, and vales—that light, and heat, and colour, appear to be distributed throughout the regions of immensity; and that these agents can hare a relation only to the necessities and the happiness of organized intelligences—that every part of nature, so far as our observations on the surface of this globe extend, appears to exist solely for the sake of sentient beings—that this doctrine Is more worthy of the Infinite Creator, and gives a more glorious and magnificent idea of his nature, than to suppose his benevolent regards confined to the globe on which we dwell. When these and a variety of other areumcnts are considered, in connexion with the wisdom and other attributes of the Deity, they amount not only to a high degree of probability, but to something approachmg to a moral demonstration. But to illustrate these arguments in a minute detail, so as to make a convincing impi ?ssion on the mind, would require a volume of a considerable size. The author flatters himself he has some original thoughts on this subject, which may probably see the light should the present work meet with public acceptance. There is no work in our language which takes an extensive view of this subject, in connexion with the attributes of the Deity, and the intimations contained in divine revelation. Fontenelle's " Plurality of Worlds" contains a number of ingenious reasonings; but he treats the subject in loo light and flippant a manner, tod without the least reference to a Supreme Intelligence. The celebrated Huygens, in his n Cotmotkeoroa" instead of attempting to prove the doctrine of a plurality of worlds, lakes it fur granted, and indulges chiefly in conjectures respecting the original structure and faculties of their inhabitants.

That the scriptures are silent on this head, has been assumed by some as a presumptive argument that this doctrine is without a solid foundation. I have already endeavoured to show that this assumption is unfounded; (see page 00.) A plurality of worlds is more than once asserted ia scripture, and in numerous passages u evidently taken for granted. Celestial intelligences are represented as ascribing "glory, bumur, wisdom, and powerH to the king of heav-ii, "because he hath created all things," and because they perceive his works to be "great and marvellous.*' But if all the great globes in the firmament were only so many frightful deserts, destitute of inhabitants, such a universe could never impire superior intelligences with admiration of the wisdom of the Creator. For wisdom consists in proportioning means to end*; but, in the case supposed, there would be no propert ion between the means and the end. The cnoans are indeed great and astonishing; but no soJ ap^Ktars to justify such a display of creating

energy. The psalmist, when uc contemplated the heavens, was so affected with the idea of the immense population of the universe, that ne seems to have been almost afraid lest he should be overlooked amidst the immensity of beings that are under the superintendence of Q-td. ** When I consider thy heavens—what is man that thou ari mindful of him!" There would be no propriety nor emphasis in this exclamation, if the heavenly orbs were devoid of inhabitants; for if no intelligent beings exist beside man, and a colony of angels, it would not appear wonderful that the Creator should exercise a particular care over the one-half of his intelligent offspring. But, if we conceive the universe as composed of tAi thousand times ten thousand worlds, peopled with myriads of intellectual beings of various orders, the sentiment of admiration implied in the passage is extremely natural and emphatic, and conveys to us an impressive idea of the intelligence, the beneficence, and the condescension of the Founder and Governor of all worlds.

No. VII. pp. 114,115.—On thejirtt Inventor of Printing.

Mr. Ireland, in his " Picturesque Tour through Holland, Brabant, and part of France, in 1789," gives the following account of the inventor of printing, when describing the city of Haerlem.

'1 Haerlem claims the invention of the art of printing. It is attributed to Lawrence Koster, an alderman of this city, in 1440; whose house is yet standing in the market-place opposite the church. Amusing himself one day in the neighbouring wood, with cutting the bark of trees into the loiters that formed the initials of his name, he is said to have laid them on paper, and falling asleep, when he awoke, observed, that from the dew, their form was impressed on the paper. This accident induced him to make further experiments: he next cut his letters in wood, and, dipping them in a glutinous liquid, impressed them on paper, which he found an improvement *, and, soon after, substituting leaden and pewter letters, erected a press in his house; thus laying the foundation of this noble art, which has thence gradually risen to its present excellence. The an, it is said, was stolen from him by his servant, John Faust us, who conveyed it to Mentz, and, from the novelty of the discovery, soon acquired the title of doctor and conjuror. The original specimens are now shown at the library in the Town Hall. The first is on a leaf of parchment, and the second and third on paper, printed only on one side, and the corners left blank for capitals. At the top are wooden cuts, representing the creation, and, as it is called, Lucifer's Fall."—Pp. 109—1 \

No. VIH. p. 118.—On Telescopes; with a brief notice of a Hew Reflecting Telescope, constructed by the author.

It is doubtful to what particular individual we owe the invention of the telescope. Some have supposed that Roger Bacon and Baptisia Porta invented this instrument. Borelii ascribes the invention to Zacharias Jansen, a native of Mi'JdLeburgh. Perhaps the account given in the ariicie to which this note refers, and which is stated by a variety of authors, may be as probable as any other. It is certain that the telescope was not in general use until the beginning of the 17th century, and that no discoveries in the heavens were made with it, till the year 1609.

There are two kinds of telescopes, refracting and reflecting. In refracting telescopes, the rays of light pass through convex or concave glasses or lenses. The object-glass is always convex, and forms an image or picture of the object in an inverted position in its focus ; which image is viewed by tho eye-glass; and the magnifying power is in the proportion of the focal distance of the object-glass to that of the eye-glass. The focal distance of a convex glass may be ascertained by holding it in the rays of the sun, opposite to a piece of white paper, and measuring the distance between the glass and the white spot, or burning point, formed on the paper^ An astronomical telescope for viewing celestial objects may be constructed with only two glasses. If an object-glass, 30 inches focal distance, be fixed in the end of a tube, and an eye-glass of one inch focus be placed at the other end, at the distance of 31 inches from tho 'object-glass, a telescope will be formed, which will magnify in the proportion of one to thirty, or 30 times; that is, objects seen through such a telescope will appear thirty times larger in diameter, or thirty times nearer, than to the naked eye. By such an instrument, the inequalities on the moon's surface, and some of the satellites of Jupiter, may be perceived; but when directed to land objects they will appear inverted, or turned upside down* In order to reverse the appearance of the obje,ct, two other eye-glasses are required; or, if a concave eye-glass of a similar focus be placed at 29 inches from the object-glass, the object will appear in its natural position, and the magnifying power will be the same; but the fi.*M of view will be much smaller. Astronomical telescopes of this construction were formeriy made of 120, and even of 200 feet in length, and were used without a tube; the obj'*ct-g1ass being placed on the top of a long pole; but these are now entirely superseded by achromatic telescopes. In the achromatic telescope, the object-glass is compounded of two, and sometimes of three lenses, placed close to each other, one of which is a double concave of white flint glass, and the other a double convex

of crown glass. By this means an image n

formed without being blended with the prismatic colours; and it will, therefore, bear a much greater magnifying power than a common refractor. An achromatic telescope four feet long will magnify objects as much as a common refractor 100 feet long.

In reflecting telescopes the images of objects are formed by speculums or mirrors, instead of lenses. They are of two kinds, the Gregorian and the Newtonian, The Gregorian reflector consists of a tube, in which a concave mirror, having a hole in its centre, is placed. The rays of light from distant objects falling upon this mirror, form an image before it, in its centre or focus. This image is intercepted by a smaller mirror, which reflects it back through the hole in the targe mirror, to an eye-glass, through which the observer views the object. In the Newtonian reflector, a plane mirror, placed at an angle of 45degrees, is substituted in place of the small mirror in the Gregorian construction, and ths observer looks down upon the object through the side of the tube. Dr. Brewster has suggested an interesting improvement in the construction of this instrument, which is described in thg Edinburgh Ency. Art. Optics, p. 644.

iVeu? Refector.—About three years ago, the author commenced a series of experiments on reflecting telescopes; and has lately constructed several on a new plan and principle. In this construction, there is no small speculum, either plane, convex, or concave; there is no tube, except a short one of two or three inches in length, for holding the speculum. The observer sits with his back to the object, and views the image formed by the speculum through an eye-piece, which requires to be nicely directed and adjusted. Three or four instruments of misconstruction have been fi1ted up, with specula of 5, 8,16, 2S, 35, and 49 inches focal distance. One of them, having a speculum of eight inches focus, and two inches diameter, with a terrestrial eye-piece, magnifying about 25 times, forms an excellent parlour telescope for viewing land objects, and exhibits them in a brilliant and novel aspect. When compared with a Gregorian of the same size and magnifying power, the quantity of light upon the object appears nearly doubled, and the image is equally distinct. It represents objects in their natural colours, without that dingy and yellowish tinge which apnears when looking through s Gregorian. Another of these instruments, having a speculum of 28 inches focal distance, and an eye-piece producing a magnifying power of about 100 times, serves as an excellent astronomical telescope. By this instrument the belt* and satellites of Jupiter, the ring of Saturn, and the mountains and cavities of the moon, may ba contemplated with great ease and distinctness. By placing the pedestal on the floor of the apart* rr.ent, when the object is at a high elevation, we can view celestial phenomena with the same ease as if we were shting at a writing desk reading a book. With a magnifying power of about 40 or J0 times applied to this telescope, terrestrial ob1ecu appear extremely orient and well defined. A speculum of 49 inches focal distance, and 6i inches diameter, has lately been fitted up on the rame principle. With magnifying powers of from 100 to 160 times, it exhibits distinct and interesting views of the moon's surface, and of the ring of Saturn, and with a power of 56 times it affords a beautiful view of land objects. The specula used in these instruments are far from being good; being of a yellowish colour, and scarcely half polished, and having large holes in the centre; as they were originally intended for Gregorian reflectors; yet the brightness of vision approaches nearly to that of achromatic telescopes. The experiments which have been made on this subject demonstrate, that a tube is not necessary for a reflecting telescope, when viewing cither celestial or terrestrial objects; and, therefore, this construction of the instrument may be denominated, The Aerial Rejlector. The simplicity of the construction, and the excellence of the performance of these instruments, have been much admired by several scientific gentlemen to whom they have been exhibited. A caveat has lately been lodged at the Patent Office, in the view of taking out a patent for this construction of reflecting telescopes; and a more detailed account of it will probably soon appear in some of the scientific journals.

In the system of Optics, lately published in the Edinburgh Encyclopaedia, (one of the most luminous and comprehensive treatises which has yet appeared on this subject,) the writer, in his introduction to the account of Dr. Brewster's improvement on the Newtonian telescope, remarks :—" If we could dispense with the use of the small specula in telescopes of moderate length, by inclining the great speculum, and using an oblique, and, consequently, a distorted reflection, us proposed first by La Maire, we should consider the Newtonian telescope as perfect; and on a large scale, or when the instrument exceeds 20 feel, it has undoubtedly this character, as nothing can be more simple than to magnify, by a single eyeglass, the image formed by a single speculum. —As the front view is quite impracticablet and, indeed, has never been attempted in instruments of a small size, it becomes of great practical consequence to remove as much as possible the evils which arise from the use of a small speculum," &r.—The instruments noticed above have eftW-tuated the desirable object alluded to by this i,-sr*ertable writer; and the principle of the construction i! neither that of Dr. Herschel's front taw. nor does it coincide with that proposed by La Maire, which seems to have been a mere nuii, which was never put inte execution.

No. IX. p. 256.—On Steam Navigation.

The application of steam, as a mechanical power for impelling vessels along rivers and seas, is one of the most brilliant and useful achievements of art which distinguish the present age and seems destined to produce an important and interesting change in the general intercourse of nations. From the " Report of a Committee of Parliament," published iu 1822, it appears, that the first application of steam to the impelling of vessels was made by an Englishman, of the name of Hull, who, in 1736, obtained a patent for the invention of a steam-boat, to be moved with a crank and paddles. But it was only in 1807, that the invention was fairly brought into practical use, by Mr. Fulton, an American, who had the assistance and advice of Mr. Bell, a Scots engineer. There are now, according to Mr. Perkins' statement, about 300 steamboats on the rivers, bays, and coasts of the United States, varying in their size from 100 to 700 tons. In Britain, tht? first successful application of steam to vessels was made by the above-mentioned Mr. Bell,* who built the Comet of 25 tons, and four horses' power, to ply on the Clyde. There are now reckoned about 150 steam-boats, from 40 to 500 tons, plying on the rivers and coasts of the British isles. Glasgow, which had the honour of introducing steam navigation on this side of the Atlantic, is still the scat of its greatest activity. According to a statement given in the " Edinburgh Philosophical Journal," published in July, 1822, there were then no less than 36 steamboats, of various sizes, plying on the Clyde. Some of these, besides performing regular voyages to Inverary, Campbelton, Belfast, Liverpool, and other places, are also performing tours, during the summer months, to the Giant's Causeway, Staffa, Skye, and other ports of the Western isles, and to Inverness by the Caledonian canal. Steam-boats are also plying between Aberdeen and Leith—between Newhaven and Aberdour, Bruntisland, Kinghorn, Kirkaldy, and Dysart; and to Queenflferry, Alloa, Grangemouth, and Sterling—between, Leiih and London—Dover and Calais. One has been plying for several years on LochLomond, which enables the traveller, at a smalt expense, to take an interesting view of the diversified scenery of that beautiful lake. Five are just now plying on the Tay; two of which, with engines of 30 and 40 horse powers, and fitted up with elegant accommodations ply daily between Perth and Dundee; each of them, during

"It Is much to be regretted, and It is certainly not eonsenlal to the liberal spirit of the aee, that thla gentleman, who was among the first Inventors of steam navigation, and who has done so much to promote its success in the neighbourhood of Glasgow, has never received any public reward for his exertions, and has been left to sink Into a state apprawnlng to poverty.

most of the summer months, transporting nearly a hundred passengers at every trip.

Steam navigation, though less understood on the Continent than with us, is now beginning to make considerable progress. There are I steam-boats on the Garonne, and several on the Seine. There are two on the Lake of Geneva, and two are about to be established on the Lake Constance, and there are, besides, one or two on the Danube. It is likely, that in the course of a few years such conveyances will be established on all our friths and rivers, and the period is, no doubt, hastening on, when excursions will be taken, in such vehicles, between Europe and America. A steam-boat of 700 tons burden, and 100 horse power, has sailed regularly, summer and winter, for three or four years, between New-York and New-Orleans, a distance of 2000 miles, in an open sea. exposed to great storms; and, by many, she is preferred to the packets, not only for the certainty of making shorter voyages, but on account of greater safety. In America, steam vessels are fitted up with every accommodation and elegancy which art can devise; so as to produce, if possible, as great a variety of enjoyment to passengers on sea as on land. Mr. Church, the American consul in France, has invented a paddle, which revolves on the paddle wheel, by very simple mechanism, which is found to save power. In the United States, a new mode of constructing cabins has been lately introduced, so as to place them beyond the reach of injury from explosions of the boiler. A steam vessel of a large size haa lately been fitted up, which is intended to sail between London and Calcutta.

"Steam vessels have been built in this country of from 10 to 500 tons, and from 5 or 4 to 110 horse power. The length of the City of Edinburgh, on the upper deck, is 143 feet; and some have lately been constructed of still larger dimensions. The American steam-boats are larger than ours, and are much more used for the conveyance of merchandise. The Frontinac, which plies on the Canadian side of Lake Ontario, is 170 feet long on deck, and 32 feet broad; and the Chancellor Livingston, which plies on the Hudson, is of the same size. The velocity aimed at is generally 6 or 9 miles an hour. The proportion is, on an average, about one horse power for every four tons of burden, computed in the usual way. The velocity is found to be nearly as the square root of the power, so that an 80 horse power engine will produce only twice the velocity of one of 20 horse power. Something depends Siso on the make and size of the vessel. The "Sovereign/' of 210 tons, and 80 horse power, goes 93 miles an hour in still water; and the "James Watt," of 448 tons, and 100 horse power, is stated to go 10 miles. For the paddleboards, the rule is, that 3-lOths of a square foot

of surface should be immersed in the water for each horse power. The paddle wheels var* from 10 to 15 feet in diameter, dip from 12 to 2U inches in the water, and have about one foot ic breadih for each 10 horse power. Mr. Gladstone affirms, that so much power is wasted in displacing the water by the stroke of the board, that the velocity of ihe ship is only about one-half of that of the outer surface of the paddle-wheel.

"There are two sources of apprehension in steam-boats—fire, and the bursting of the boiler. With regard to the latter, when the boiler is of low pressure, it is satisfactorily established thai not the smallest danger exists. And in the bes' constructed vessels, the danger from fire is completely obviated, by separating the furnace from the sides of the vessels by five inches of water."

The power of steam is now rendered subservient to the breaking of stones for the construction of roads. The stones are put into a kind of hopper above, and pushed down with a rake, and the machine is worked by a rotatory motion of one horse power; and will break a ton of hard pebbles completely, in from six to eight miin tes. A steam machine has also been invented for the dressing of woollen cloth, which does as much work in 50 minutes as two men could do in two days. Man. Mag. Aug. 1823, p. 71.—A steam carriage, for conveying goods and passengers on land, wax lately constructing hy Mr. Griffiths. Its rate of motion, on common roads, is estimated at five miles an hour, at an average; about three miles when going up hill, and above seven when running down. But pecuniary embarrassments, or other impediments, have, hitherto, prevented the completion of his design.

Mr. Perkins has lately made improvements on the steam engine, which promise to carry its powers to a high degree of perfection. The engine he has lately constructed is calculated to a ten horse power, though the cylinder is no more than two inches in diameter, and 18 inches long, with a stroke of only 12 inches. Although the spare occupied by the engine is not more than six feet by eight, yet Mr. P. considers the apparatus (with the exception of the working cylinder and piston) as perfectly sufficient for a thirty horse engine. When the engine performs full work, it consumes only two bushels of coal in the day. Mr. Perkins has also announced a discovery still more extraordinary, viz. that he has been able u to arrest the heat, after it has performed its mechanical functions, and actually pump it back to the generator, to unite with a fresh portion of water, and renew its useful labours." A particular account of Perkins's engine, accompanied with an engraving, is given in the Edin. Philos. Journal, No. 17, for July 1823. The pretensions of Mr. Perkins, »owever, have not yet been so fully substantiated by experimen! as to satisfy the anxious expet ation of the imblss.

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