diameter of the orbit he would describe: and the No. II. p. 34.—Experimental illustrations of the Pressure of the Atmosphere. The pressure of the atmosphere is most strikingly illustrated by means of the air-pump. But as few persons, comparatively, possess this instrument, the following experiments, which any person may perform at pleasure, are sufficiently. convincing on this point. Take a common wine-glass, and fill it with water; apply a piece of paper over the mouth of the glass; press the paper to the rim of the glass with the palm of the hand; turn the glass upside down; withdraw the hand from the paper, and the water will be supported by the pressure of the atmosphere. That it is the atmospherical pressure, and not the paper, which supports the water, is evident; for the paper, instead of being pressed down by the weight of the water, is pressed upward by the pressure of the atmosphere, and appears concave, or hollow in the middle. If the Hame of a candle be applied to the paper, it may be held, for an indefinite length of time, close to the paper, without setting fire to it. The same fact is proved by the following expe-iment :—Take a glass tube, of any length, and of a narrow bore; put one end of it in a basin of water; apply the mouth to the other end, and draw out the air by suction; the water will immediately rise toward the top of the tube; and if the finger or thumb be applied to the top of the tube, to prevent the admission of air, and the tube removed from the basin of water, the water in the tube will be supported by the pressure of the atmosphere on the lower end. Again: ·Take a wine-glass, and burn a small bit of paper in it; and when the paper is burning The pressure of the atmosphere explains a variety of common phenomena. When we take a draught of water out of a basin, or a running stream, we immerse our mouths in the water, and make a vacuum by drawing in the air; the pressure of the atmosphere upon the external surface of the water then forces it into the mouth. The same cause explains the process of a child sucking its mother's breasts-the action of a boy's sucker, in lifting large stonesthe rise of water in pumps-the effects produced by cements the firm adhesion of snails and periwinkles to rocks and stones-the scarcity of water in the time of hard frosts-and the fact that a cask will not run by the cock, unless a hole be opened in some other part of the cask. No. III. p. 118.-On the means by which it may probably be ascertained whether the Moon be a Habitable World. About six years ago, the author published, in the Monthly Magazine, a few observations on the surface of the moon, in which a few remarks were offered on this subject. The following is an extract from that communication: Were a "If we be ever to obtain an ocular demonstration of the habitability of any of the celestial orbs, the moon is the only one, where we can expect to trace, by our telescopes, indications of the agency of sentient or intelligent beings; and I am pretty much convinced, that a long continued series of observations on this planet, by a number of individuals in different places, might completely set at rest the question, 'Whether the moon be a habitable world?' vast number of persons, in different parts of the world, to devote themselves to a particular survey of the moon-were different portions of her surface allotted to different individuals, as the object of their particular research—were every mountain, hill, cavern, cliff, and plain accurately inspected-and every change and modification in the appearance of particular spots carefully marked and represented in a series of delineations, it might lead to some certain conclusions, both as to her physical constitution, and her ultimate destination. It can be demonstrated, that a telescope which magnifies 100 times, will show a spot on the moon's surface, whoso diameter is 1223 yards; and one which magnifies a thousand times, will, of course, enable us to perceive a portion of her surface, whose size is only 122 yards: and, consequently, an object, whether natural or artificial, of no greater extens exciting, among the bulk of mankind, a general attention to such investigations. But were this object accomplished, and were numerous observations made from the tops of mountains, and in the serene sky of southern climes, where the powers of the telescope are not counteracted by dense vapours, there can be little doubt that direct proofs would be obtained that the moon is a habitable world; or, at least, that the question in relation to this point would be completely set at rest. very of a Lunar Fortification. than one of our large edifices, (for example, St. Paul's church, London,) may, by such an instrument, be easily distinguished. Now, if every minute point on the lunar surface were accurately marked by numerous observers, it might be ascertained whether any changes are taking place, either from physical causes, or from the operations of intelligent agents. If a large forest were cutting down-if a city were building in an open plain, or extending its foriner boundaries-if a barren waste were changing into a scene of vegetation-or, if an immense concourse of animated beings were occasionally No. IV.-Remarks on the late pretended disov assembled on a particular spot, or shifting from one place to another-such changes would be indied by certain modifications of shade, colou, or motion; and, consequently, would furnish a direct proof of the agency of intelligent beings analogous to man, and of the moon being a habitable globe. For although we may never be able to distinguish the inhabitants of the moon, (if any exist,) yet if we can trace those effects which can flow only from the operations of intelligent agents, it would form a complete demonstration of their existence, on the same ground on which a navigator concludes an unknown island to be inhabited, when he perceives numan habitations, and cultivated fields. "That changes occasionally happen on the lunar hemisphere next the earth, appears from the observations of Horschel and Schroeter, particularly from those of the latter. In the transactions of the 'Society of Natural Philosophy,' at Berlin, Schroeter relates, that on the 30th December, 1791, at five o'clock, P. M.with a seven, feet reflector, magnifying 161 times, he perceived the commencement of a small crater on the south-west declivity of the volcanic mountain in the Mare Crisium, having a shadow of at least 2' 5. On the 11th January, at twenty minutes past five, on looking at this place again, he could see neither the new crater nor its shadow. Again, on the 4th January, 1792, he perceived, in the eastern crater of Helicon, a central mountain, of a clear gray colour, 3' in diameter, of which, during many years' obser• This apvations, he had perceived no trace. pearance,' he adds, 'is remarkable, as probably from the time of Hevelius, the western part of Helicon has been forming into its present shape, and nature seems, in that district, to be particularly active.'-In making such minute observations as those to which I allude, it would be proper, along with an inspection of the moon's luminous disk, to mark the appearances of different portions of her dark hemisphere, when it is partially enlightened by the reflected light from the earth, soon after the appearance of new The British public was lately amused by the announcement of a discovery said to have been made by Professor Frauenhofer, of Munich. This gentleman was said to have discovered a fortification in the moon, and to have distinguished several lines of road, supposed to be the work of the lunar inhabitants. It is scarcely necessary to say, that such announcements are obviously premature. To perceive distinctly the shape of an object in the moon, which resembles a fortification, it is requisite, that that object be of a much larger size than our terrestrial ramparts. Besides, although an object resembling one of our fortifications were perceived on the surface of the moon, there would be no reason to conclude, that it served the same We are purpose as fortifications do among us. so much accustomed to war in our terrestrial system, and reflect so little on its diabolical nature, that we are apt to imagine that it must form a necessary employment even in other worlds. To be assured that a fortification existed in the moon for the same purpose as with us, would indeed be dismal tidings from another world; for it would be a necessary conclusion, from such intelligence, that the inhabitants of that globe are actuated by the same principles of depravity, ambition, and revenge, which have infected the moral atmosphere of our sublunary world. With regard to the pretended discovery of the lunar roads, it may not be improper to remark, that such roads behooved to be at least 400 feet broad, or ten times the breadth of ours, in order to be perceived as faint lines through a telescope which magnifies a thousand times; which is a higher power, I presume, than Frauenhofer can apply with distinctness to any of his telescopes. It is not at all likely that the lunar inhabitants are of such a gigantic size, or employ carriages of such an enormous bulk, as to require roads of such dimensions, since the whole surface of the moon is only the thirteenth part of the area of our globe. Schroeter conjectures the existence of a great city to the north of Marius, (a spot in the moon,) and of an extensive canal towards Hygena, (another spot,) and he represents part of the spot naneu Mare Imbrium, to be as fertile as the Campania. See Edin. Phil. Jour. No. 21, for July, 1824. Similar remarks to those now stated will apply to these conjectures of Schroeter. We are too apt to imagine, that the 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 expressed by numbers. See pp. 44, 46. In the pages referred to, and other parts of this volume, some very large numbers are expressed in figures. Some readers have insinuated, that it would have been better to have expressed such numbers in words. The author, however, is of a different opinion; because to some readers, not much acquainted with numeration, a thousand trillions would convey nearly the same idea as a thousand nonilions, though the one number contains 58 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 5828 years have elapsed 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 miles, then this distance may be otherwise expressed, by saying, that the number of miles which intervene between us and these bodies is more than a hundred times greater than the number of moments which have elapsed since the creation; and, by a similar comparison, it will be found that the number of cubical miles within the limits 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 sep tillions 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 as a standard for estimating the number of cubical miles contained within the space which intervenes between us and the nearest stars, 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. -hall 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 minds like ours can approximate to an idea of the infinity of the Creator. And if an image 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! 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 full 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 to the planets of our system, there are many circumstances which bear a striking resemblance to the constitution of our globe and its appenaages. they have annual and diurnal motions, energy. The psalmist, when ne conternpiated 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 God. "When I consider thy heavens-what is man that thou art 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 ten 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. moons, atmospheres, mountains, and vales-that ight, and heat, and colour, appear to be distributed throughout the regions of immensity; and that these agents can have 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 arguments 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 approaching to a moral demonstration. But to illustrate these arguments in a minute detail, so as to make a convincing impression 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 acroptance. There is no work in our language No. VII. pp. 114, 115.—On the first Inventor of 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 too light and flippant a manner, and without the least reference to a Supreme Intelligence. The celebrated Huygens, in his "Cosmotheoros," instead of attempting to prove the doctrine of a plurality of worlds, takes it for 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 90.) A plurality of worlds is more than once asserted in scripture, and in numerous passages is evidently taken for granted. Celestial intelligences are represented as ascribing "glory, honour, wisdom, and power" to the king of heaven, "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 inspire superior intelligences with admiration of the wisdom of the Creator. For wisdom consists in proportioning means to ends; but, in the case supposed, there would be no proportion between the means and the end. The means are indeed great and astonishing; but no end appears to justify such a display of creating 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. "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 letters 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 art, it is said, was stolen from him by his servant, John Faustus, 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. VIII. p. 118.-On Telescopes; with a brief notice of a NEW REFLECTING TELESCOPE, constructed by the author. It is doubtful to what particular individual we owe the invention of the telescope. Some nave supposed that Roger Bacon and Baptista Porta invented this instrument. Borelli ascribes the invention to Zacharias Jansen, a native of Middleburgh. Perhaps the account given in the article 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 the 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 the 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 or, be perceived; but when directed to land objects they will appear inverted, or turned upside down. In order to reverse the appearance of the object, two other eye-glasses are required; 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 in its natural position, and the magnifying power will be the same; but the field of view will be much smaller. Astronomical telescopes of this construction were formerly made of 120, and even of 200 feet in length, and were used without a tube; the object-glass 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 is 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 large mirror, to an eye-glass, through which the observer views the object. In the Newtonian reflector, a plane mirror, placed at an angle of 45 degrees, is substituted in place of the small mirror in the Gregorian construction, and the 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 the Edinburgh Ency. Art. Optics, p. 644. New Reflector.-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 this construction have been fitted up, with specula of 5, 8, 16, 28, 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 appears when looking through a 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 belts and satellites of Jupiter, the ring of Saturn, and the mountains and cavities of the moon, may be contemplated with great ease and distinctness. By placing the pedestal on the flour of the apart. |