and other globes much larger than ours, move Venus. I have sometimes illustrated this argument, round their axes in a shorter period-that in all the with peculiar effect, by means of an equatorial teleother works of Omnipotence, means apparently the scope, and a common planetarium. By the equatomost simple are selected to accomplish the most rial telescope, with a power of 60 or 80 times, most grand and magnificent designs-and that there is no of the stars of the first magnitude, and some of those example known to us, throughout the universe, of of the second, may be seen even at noonday. Venus a larger body revolving around a smaller. When may be seen by this instrument, in the day time, such considerations are fully and familiarly illus- during the space of nineteen months, with the intertrated, the pupil will soon be made clearly to per- ruption of only about thirteen days at the time of ceive, that the rotation of the earth must necessarily her superior conjunction, and three days at the time be admitted, and that it will fully account for all of her inferior, so that the phase she exhibits may the diversity of diurnal motion which appear in the be seen almost every clear day. Having placed the sun and moon, the planets and the stars. Earth and Venus in their true positions on the plaThe annual revolution of the earth, and its posi-netarium, by means of an Ephemeris or the Nautition in the solar system, might be proved and illus- cal Almanack, I desire the pupil to place his eye in trated by such considerations as the following:- a line with the balls representing these planets, and that if this motion did not exist, the motions of all to mark the phase of Venus as seen from the earththe planets would present a scene of inextricable whether a crescent, a half-moon, or a gibbous phase. confusion, consisting of direct and retrograde mo- I then adjust the equatorial telescope for Venus, if tions, and looped curves, so anomalous and irregu- she is within the range of our view, and show him lar, as to be inconsistent with every thing like har- the planet with the same phase in the heavens. This mony, order, or intelligence-that Mercury and exhibition never fails to gratify every observer, and Venus are observed to have two conjunctions with to produce conviction. But it can seldom be made, the sun, but no opposition; which could not happen if we must wait till the planet be visible to the unless the orbits of these planets lay within the orbit naked eye, and capable of being viewed by a comof the earth--that Mars, Jupiter, and the other su- mon telescope; for it is sometimes invisible to the perior planets, have each their conjunctions with naked eye, for nearly one half of its course from and oppositions to the sun, which could not be un-one conjunction to another. Besides, the phases of less they were exterior to the orbit of the earth-that this planet are more distinctly marked in the day the greatest elongation of Mercury from the sun is time, when near the meridian, than either in the only about 20 degrees, and that of Venus 47; but if morning or evening, when at a low altitude, in the earth were the centre of their motions, as the which case it appears glaring and undefined, on ac Ptolemaic system supposes, they might sometimes count of the brilliancy of its light, and the undulatbe seen 180 degrees from the sun, which never hap-ing vapors near the horizon, through which it is pens-that some of the planets appear much larger seen. As actual observations on the planets in the and brighter at one time than at another, on account heavens make a deeper and more convincing imof their different distances from the earth; but, on pression on the mind of a young person, than mere the other hypothesis, their brilliancy should be al-diagrams or verbal explanations, I consider an equaways the same-that Mercury and Venus, in their torial telescope, in conjunction with a celestial superior conjunctions with the sun, are sometimes globe and an orrery, as essentially necessary to hid behind his body, and in their inferior conjuc- every teacher of astronomy; as, independently of tions sometimes appear to pass across the sun's disk, its use, now hinted at, it is the best and most comlike round black spots, which would be impossible prehensive instrument for conveying an idea of the according to the Ptolemaic system;-and, in short, practical operations of this science. It may be made that the times in which the conjunctions, oppositions, to serve the general purposes of a transit instrustations, and retrogradations happen, are not such ment, a quadrant, an equal altitude instrument, a as they would be if the earth were at rest, but pre- theodolite, an azimuth instrument, a level, and an cisely such as would happen, if the earth move accurate universal sun-dial. It serves for taking the along with all the other planets, in the stations and right ascensions and declinations of the heavenly periods assigned them in the system which has the bodies, and for conveying a clear idea of these opesun for its centre. From such considerations, when rations. It may be made to point to any phenomeproperly explained, the annual motion of the earth, non in the heavens whose declination and right asand its relative position in the system, may be cension are known; and, in this way, the planets clearly demonstrated, and the pupil made to per- Mercury, Herschel, Ceres, Pallas, Juno, and Vesta, ceive the beauty and harmony of the celestial mo- a small comet, or any other body not easily distions, and the necessity of having the great source tinguished by the naked eye, may be readily pointed of light and heat placed in the centre of the system. out.* For as the sun is intended to cheer and irradiate The cause of the variety of seasons may next be surrounding worlds, it is from the centre alone that explained and illustrated. It is difficult, if not imthese agencies can be communicated, in a uniform possible, by mere diagrams and verbal explanations, and equable manner, to the planets in every part of to convey a clear idea on this subject; and therefore, their orbits. Were the earth the centre, and the some appropriate machinery must be resorted to, in sun and planets revolving around it, the planets,order to assist the mind in forming its conceptions when nearest the sun, would be scorched with ex-on this point. The difficulty is, to conceive how cessive heat, and when farthest distant, frozen with excessive cold.

the sun can enlighten the North Pole without intermission, during one half of the year, and the South Pole during the other, while the poles of the earth never shift their position, but are directed invariably to the same points of the heavens. This is fre

There is another consideration by which the earth's annual revolution and its position in the system are demonstrated;-and that is, that the planets Mercury and Venus, when viewed through good telescopes, are found to assume different phases, * A small Equatorial, having the horizontal, Dein different parts of their orbits; sometimes appear-clination, and Equatorial circles about six inches ing gibbous, sometimes like a half-moon, and at diameter, surmounted with a twenty-inch achromaother times like a crescent, and a full enlightened tic telescope, with magnifying powers of from 30 to hemisphere, which could never happen if they re- 80 times, may be procured for about fifteen or sixvolved round the earth as their centre, and if the teen guineas, which will serve every general purearth was not placed in an orbit exterior to that of pose in teaching astronomy.

quently attempted to be illustrated by means of a for this purpose less than 34 feet Achromatic, with brass hoop with a candle placed in its centre, and a powers varying from 40 to 180 or 200 times.* A small terrestrial globe carried round it, having its power of 150 is a very good medium for inspecting axis inclined to the brass circle, which is intended all the more interesting phenomena of the heavens. to represent the orbit of the earth. But this exhi- With this power, distinct and satisfactory views bition requires some dexterity to conduct it aright, may be obtained of the solar spots, the phases of and after all is not quite satisfactory. An orrery, Mercury, Venus, and Mars, the belts, and sometimes having all the requisite movements by wheel-work, the spots of Jupiter, and the shadows of his saleland where the Earth moves with its axis parallel lites, the ring and some of the moons and belts of to itself and inclined to the plane of the ecliptic, is Saturn, the spots of Mars, the minute hills and the best instrument for illustrating all the variety cavities of the moon, several of the double stars, of the seasons. When such a machine cannot be and many of the most remarkable nebula. To perprocured for this purpose, its place may be supplied ceive distinctly the division of Saturn's ring, reby a neat little instrument, called a Tellurian, which quires a power of at least 200 times. In exhibiting has been manufactured for many years past by such objects to the young, especially when the lower Messrs. Jones, Holburn, London, and may be pur-powers are used, some attention is requisite to adchased for about thirty shillings. This instrument just the instrument to distinct vision, as their eyes consists of a brass ball representing the sun-which are generally more convex than the eyes of permay be occasionally screwed off, and a lamp substi- sons advanced in life, and those who are shorttuted in its place-an ivory ball representing the sighted will require an adjustment different from earth, having the circles of the sphere drawn upon that of others. Unless this circumstance be attendit, a small ball representing the moon, and about ed to, their views of celestial phenomena will eight, wheels, pinions and circles. It exhibits the frequently be unsatisfactory and obscure. In exhiannual motion of the earth, and the moon revolv-biting the surface of the moon, the period of halfing around it, with its different phases, the cause moon, or a day or two before or after it, should geof eclipses, the retrograde motion of the moon's nerally be selected; as it is only at such periods nodes, and the inclination of its orbit to the plane that the shadows of the mountains and vales, and of the ecliptic. The earth is moveable on an axis the circular ridges, can be most distinctly perceived. inclined 23 degrees to the ecliptic, and its axis At the time of full moon, its hemisphere presen's preserves its parallelism during its course round only a variegated appearance of darker and brighter the sun. The seasons are exhibited on this instru- streaks, and no shadows are discernible; so that, ment as follows:-The index, which points out the from the telescopic appearance of the full moon, sun's place and the day of the month, is placed at we could scarcely determine whether or not its sur the 21st March, the time of the vernal equinox, face were diversified with mountains and vales. and the north and south poles of the earth are placed exactly under the terminator, or boundary bePrevious to exhibiting the moon through a teletween light and darkness. When the machinery scope, it may be proper to give the observers an is moved by the hand till the index points to the 21st idea of some particular objects they will see, on June, the time of the summer solstice, then the which their attention should be fixed, and from North Polar regions appear within the boundary of which they should deduce certain conclusionslight, and the South Polar within the boundary of For, a view of the moon, for the first time, through darkness. Turning the machine till the index a powerful telescope, is apt to overpower the ere, points to September 23d, both poles again appear As one of the peculiarities of the lunar surface conand to produce a confused and indistinct perception. on the boundary of light and darkness. Moving it on to December 21st, the Arctic circle appears in sists in the numerous cavities, and plains surrounddarkness, and the Antarctic in the light. During ed with circular ridges of mountains, and insulated these motions, the earth's axis keeps parallel to it mountains rising from a level surface-an idea of self, pointing uniformly in the same direction. the shadows and circumstances by which these obThis exhibition is quite satisfactory and convincing;jects are indicated should be previously communithe only objection to the instrument is, that it is cated. This may be done by means of a saucer, small,-about eight or nine inches diameter-and, the top of a small circular box, or any other object consequently will admit only four or five individuals which may represent a plain surrounded by a cirat a time to inspect its movements with distinctness.cular ridge. In the middle of any of these objects A full and specific description should next be given of all the facts connected with the solar system-the distances and magnitudes of the sun and planets-their annual and diurnal revolutions-the solar spots-the belts and satellites of Jupiter-the rings of Saturn-the phases of Venus-the spots of Mars, and the mountains and cavities of the Moon. After which some details might be given of the facts which have been ascertained respecting comets, variable stars, double and treble stars, new stars, stars once visible which have disappeared, and the numerous nebula which are dispersed through different regions of the heavens. The pupils should now be gratified with a view of some of these objects through good telescopes. A telescope, magnifying about 30 times, will show the satellites of Jupiter, the crescent of Venus, the solar spots, and the rugged appearance of the Moon.-❘ With a magnifying power of 60 or 70, the ring of Saturn, the belts of Jupiter, the shadows of the lunar mountains and cavities, and all the phases of Venus, may be distinguished. But the views of these objects obtained by such magnifying powers are unsatisfactory. No telescope should be selected

may be placed a small peg to represent a mountain. Then placing a candle at the distance of a foot or two, so as to shine obliquely upon the objects, the inside of the circular dish farthest from the candle will be seen enlightened, while a considerable portion of the bottom will be covered by the shadow thrown upon it by the side next the candle, and the shadow of the peg will be seen verging towards the enlightened side. This previous exhibition will give them an idea of the form of some of the mountains and vales on the lunar surface, and enable them to appreciate the nature of those striking inethe dark and enlightened parts of the moon. Other qualities which appear near the boundary between objects which diversify the moon's surface may be represented and illustrated in a similar manner, and sufficient time should be allowed to every observer for taking a minute inspection of all the varieties

* An Achromatic telescope of this description, with an object-glass, 45 inches focal distance, and about 3 inches diameter, with 4 or 5 magnifying powers, with a brass tube mounted on a brass tripod, may be purchased, in London, for 25 guineas.

on the lunar disk. The solar spots may be viewed 4 feet, Saturn; and, at 95 inches, or about 8 feet inches, or with ease, by interposing a colored glass between from the sun's ball, place one to represent Herschel. the eye and the image of the sun; but, in looking This will convey a pretty correct idea of the prothrough the telescope in the ordinary way, they can portional distances from the sun of the principal be perceived by only one individual at a time. In primary planets. The distances of Ceres, Pallas, order to exhibit them to a company of 30 ur 40 per- Juno, and Vesta, might likewise be represented, if sons at once, the image of the sun may be thrown judged expedient; but as their orbits are more econ a white wall or screen. I have generally exhi-centric than those of the other planets, and some bited them in the following manner. To a 34 feet Achromatic telescope, I apply a diagonal eye-piece which has a plain metallic speculum placed at half a right angle to the axis of the telescope. By this eye-piece, after the room has been darkened as much as possible, the image of the sun I his spots is thrown upon the roof of the apartment, which and some of the constellations, may be represented forms a beautiful circle of light, and exhibits all the spots which then happen to diversify his surface. His apparent diurnal motion is also represented, along with the motions of any thin fleeces of clouds which may happen to cross his disk. In this way, too, the proportional magnitudes of the spots may be measured, and compared with the diameter of the sun, and, of course, their real magnitudes ascertained.

of them cross each other, they cannot be accurately represented. When orreries or telescopes cannot be procured for exhibiting the celestial motions and phenomena to which I have alluded, some of these objects, such as the rings of Saturn, the belts and moons of Jupiter, the phases of Venus, the Moon, in a dark room by means of the phantasmagoria. But the representations made by this instrument form but a rude and paltry substitute for the exhibitions presented by the orrery and the telescope, and need never be resorted to, except for amusement, where these instruments can be obtained.

It might next be expedient to communicate to the pupil an idea of the nature of a parallax, to prepare him for understanding the mode by which the dis tances and magnitudes of the heavenly bodies are ascertained. This might be done by fixing a pole or staff, with a pointed top, in a garden or large area, opposite a wall or hedge, F G, Fig. 1, and, desiring one of the pupils to take his station at A, and another at B, and to direct their eyes to the points on the wall which appear in a line with the top of the pole, when the one stationed at A will

Fig. 1.

B

In illustrating the phenomena of the planetary system by means of orreries, planetariums, and lunariums, great care should be taken to guard the young against the false and imperfect conceptions of the magnitudes and distances of the planets, which such instruments have a tendency to convey. No orrery, of a portable size, can represent, at the same time, both the proportional distances and relative magnitudes of the different planets. Even those large machines designated Eidouraniums and Transparent Orreries afford no correct views of these particulars; and some of them convey very erroneous and distorted conceptions of the relations of the solar system, where it is the chief design to dazzle the eye with a splendid show. In some of these exhibitions I have seen the stars represented as if they had been scattered through different parts of the planetary system. An orrery representing the proportional distances and magnitudes of the sun and planets would require to be more than three u miles in diameter; and, even on this scale, Jupiter would be less than 3 inches diameter, the Earth a quarter of an inch, or about the size of a small pea, and Mercury only about the dimensions of the head of a small pin, while the sun would require to be represented by a ball 30 inches in diameterin which case all the planets would be invisible from the centre of the system. To correct, in some perceive it to coincide with the point C, and the measure, the erroneous ideas which a common or other stationed at B will perceive it at D. They rery is apt to convey, the magnitudes and distances may be told that C D is the parallax, or the dif should be separately represented. Suppose a celes- ference of the apparent place of the pole P, when tial globe, 18 inches in diameter, to represent the viewed from the positions A and B, which is meaSun, Jupiter will be represented by a ball about 14 aured by the angle C P D; and that, if the distance inch diameter, Saturn by one of 13 inch, Herschel between A and B were measured, and the number by one about inch, the Earth by a ball of of degrees or minutes in the angle C P D or APB inch, or somewhat less than a small pea, Venus by of the stations can be easily determined. This ascertained, the distance between the pole and any a bail of nearly the same size, Mars by a globule may be easily applied to the case of the heavenly of about inch, Mercury by a globule of and bodies by means of such a diagram as Fig. 2, where the Moon by a still smaller globule of inch in H I K represents the Earth, M the Moon, Pa diameter. These three last might be represented planet, and S T a quadrant of the starry heavens. by three different sizes of pin-heads. When balls It is evident, that, if the moon be viewed from the of these sizes are placed adjacent to an 18-inch surface of the earth at H, she will appear in the globe, and compared with it, an impressive idea is heavens at the point a; but if she be viewed from conveyed of the astonishing magnitude of the sun, the centre C, she will be seen at the point b, the which is 500 times greater than all the planets, satel-angle a Mb being the angle of parallax. This lites, and comets, taken together. The proportional angle being found, which is the same as the angle distances may be represented as follows. At one H M C, and the base line H C, or the earth's end of a table 9 feet in length, fix a ball upon a pil-semidiameter being known, which is nearly 4000 lar to represent the sun; at 2 inches from the sun's miles-the length of the line H M, or the distance ball, place another, to represent Mercury; at 3 of the moon, can be easily determined. It may be inches, Venus; at 5 inches, the Earth; at 7 inches, proper also to state, that the farther any heavenly Mars; at 25 inches, Jupiter; at 474 inches, or about body is distant from the earth, the less is its parallax.

1:

15'

Hence the parallaxes of the sun and planets are all | spect to all terrestrial objects. This subject may much less than that of the moon, which is the nearest soon be rendered quite plain to the pupil, by familiar celestial body to the earth. Thus, the parallax c d illustrations, in connection with a few instructions of the planet P is less than that of the Moon, M, on the nature and properties of triangles, and the and the same principle likewise holds true with re- first principles of trigonometry.

I have been somewhat particular in some of the stances of man, when we consider uis comparative hints thrown out above, because it is of some import- ignorance, and the low station which he holds in the ance that the young should have clear and impres- scale of creation-and the reasonableness of culti sive conceptions of every object presented to their vating a spirit of humility in the presence of that Alview, in every step of their progress on this subject, mighty Being whose "glory is above the heavens," and not depend merely on the assertions or the po- and whose kingdom ruleth over all," when we sitions announced by their teachers; and because consider, that, when compared with the myriads of such a train of observations and experimental illus- more exalted intelligences that people the universe, trations has seldom been attended to, in attempting we are only like a few atoms in the immensity of to convey to the juvenile mind a popular view of the space. He may direct their attention to the infiniteleading facts of astronomy. After the pupil has ly diversified scenes of grandeur and felicity which acquired a knowledge of the subjects to which I have the universe must contain, since its range is so exadverted, an intelligent teacher will find little diffi-tensive and its objects so magnificent; and to the culty in gradually unfolding to him the doctrines evidence which these facts afford, that the Creator and facts in relation to solar and lunar eclipses-the has it in his power to gratify his rational offspring tides the form of the planetary orbits-the nature with new objects, and new sources of enjoyment, of refraction-the divisions of time-the mensura- during every period of infinite duration. In short, tion of the earth-centrifugal and centripetal forces-- he may excite them, from such considerations, to a the circles of the celestial sphere-and various other pire after that more glorious state of existence where particulars connected with astronomical science. the works of Omnipotence will be more fully unIn illustrating the principles and exhibiting the ob-folded, and to cultivate those holy principles and jects of astronomy, the pious and intelligent teacher dispositions which will qualify them for mingling will have frequent opportunities of impressing upon in the society and engaging in the employments of the minds of his pupils the most sublime ideas of the heavenly world. Such instructions, when amalthe Perfections of the Creator, and of the Extent gamated with Christian views and motives, could and Grandeur of his Empire, and of inspiring them not fail of producing a beneficial impression on the with Love, Admiration, and Reverence; and such susceptible hearts of the young, which might, in opportunities ought never to be neglected. When some measure, influence their conduct and train of descanting on the number and magnificence of the thought through all the remaining periods of their celestial worlds, he may very appropriately take oc- lives.* casion to impress them with the idea of the littleness of this earth, and its comparative insignificance, when placed in competition with the numerous and more resplendent worlds and systems which compose the universe; and, consequently, with the folly and madness of ambition, and of all those warlike schemes and ferocious contentions, of which our world has been the melancholy theatre. He may occasionally expatiate a little on the folly of pride, and its inconsistency with the character and circum

* The most celebrated writers on Astronomy are Long, Ferguson, La Caille, Martin, O. Gregory, Visce, Herschel, Robison, La Lande, La Place, Biot, and various others. Popular works on this subject, which may be put into the hands of young persons, are such as the following:-Ferguson's "Gentleman and Lady's Astronomy"--Martin's “Gentleman and Lady's Philosophy," Vol. 1.Bonnycastle's "Introduction to Astronomy" Mrs.

In the department of Mechanics,-illustrations might be given of the mechanical powers, which are

generally arranged under the heads of the lever, the pulley, the wheel and axis, the inclined plane, the wedge, and the screw. A simple apparatus for illus

The object of Natural and Experimental Philoso-trating these powers could easily be constructed by phy is to investigate the phenomena of the material an ingenious mechanic, at a trifling expense, and world, in order to discover their causes, and the might be rendered conducive both to the entertainlaws by which the Almighty directs the movements ment and instruction of the young. In particular, of the universe; and to apply the observations and the nature and power of the lever, and the principle discoveries we make to useful purposes in human on which it acts, should be minutely explained, by life, and to expand our views of the perfections and experimental illustrations, and by showing its efoperations of the Creator. This department of study fects in the common operations of life. A long bar has generally been divided into the following subor- of iron or hard wood might be erected on a steady dinate branches, Mechanics, Hydrostatics, Hydrau-fulcrum, and placed in the area adjacent to the lics, Pneumatics, Meteorology, Acoustics, Optics, Elec- school, which might serve both for amusement and tricily, Galvanism, and Magnetism. This is a sub- for illustrating the power of the lever. This bar ject, the popular and experimental parts of which might be divided into feet or half feet, or any conmay be rendered highly entertaining and instructive venient number of equal parts, and so constructed to the minds of the young. But, however import- that any of those parts might be placed upon the ant the subject in all its branches may be to the re- fulcrum. By such a lever the different powers to gular scientific student, it would be inexpedient to be applied at different distances from the fulcrum, attempt conveying more than a general view of the when a weight is to be raised, might be familiarly more popular parts of it to young persons from the illustrated. A seat or swing might be fixed at one age of ten to the age of fourteen, although many of end of the beam on which a boy might sit, while the experiments connected with it may, with pro- some of his companions, towards the other end, appriety, be exhibited even to children of an earlier plied different powers or weights at different disage, in order to excite a taste for the study of natural tances from the fulcrum, as a counterpoise; which science. Experimental illustrations of the subjects would suggest various calculations respecting the of Natural Philosophy sometimes require an exten-powers requisite to be applied in any given case, sive apparatus, which cannot be procured but at a according to the distance from the point of support. considerable expense; but there are many interest- It will tend to excite their interest in this subject, ing experiments, illustrative of scientific principles when they are informed that scissors, pincers, snuf and facts, which can be performed with very sim- fers, oars, the balance, the see-saw, doors turning on ple apparatus, and at little expense; and all that I hinges, the rudders of ships, cutting-knives fixed at propose, under this article, is to suggest a few of one end, and the bones of the arm, are all so many those experiments which almost every teacher may different kinds of levers, and that the operations of have it in his power to perform. quarrying stones, raising great weights, poking the fire, rowing a boat, digging the ground, and such like, are all performed on the principle of this mechanical power. Similar contrivances might be Bryan's "Astronomy"-"The Wonders of the adopted for illustrating the wheel and axle, and other Heavens"-Gregory's "Astronomical Lessons," &c. powers. A knowledge of the mechanical powers But none of these works is adapted to the purpose may be useful to every individual, whatever may of teaching. The best treatise of this kind I have be his trade or profession in future life, but particu seen, calculated to be a text-book for an intelligent larly to those who may afterwards engage in the teacher, is a work entitled "The Geography of the arts of carpentry, architecture, mining, engineering, Heavens," by Elijah H. Burritt, A. M., lately pub- and other operations where a knowledge of the me lished at Hartford, State of Connecticut. This vo- chanical powers is essentially requisite; and the imlume comprises 342 closely printed pages, large pressions made upon their minds in early life by fa18mo, and several appropriate wood-cuts. It con-miliar illustrations of these powers, would tend to tains a very full and lucid description of all the particulars respecting the different constellations and principal stars, the general principles of astronomy, the facts connected with the solar system, problems, astronomical tables, and almost every thing that can be deemed interesting to the general student. Every page contains Questions, as exercises for the judgment of the pupil. It is accompanied by a large and beautiful Atlas, 16 inches by 14, containing 7 Planispheres, or Maps of the Heavens: 1. The visible heavens in October, November, and December. 2. D. in January, February, and March. 3. Do. in April, May, and June. 4. Do. in July, August, and September. 5. The visible heavens in the North Polar Regions for each month of the year. 6. Do. in the South Polar Regions. 7. Planisphere of the whole heavens on Mercator's projection.— "The first four maps are so constructed, that the pupil in using them must suppose himself to face the south, and to hold them directly over head, in such a manner that the top of the map should be towards the north, and the bottom towards the south." In the construction of these maps, and in the composition of the work, the latest discoveries have been carefully inserted. This work, since its first publication in 1833, has had an extensive sale in the United States, and been introduced into many respectable seminaries.

facilitate their study of such subjects when they became the more particular objects of their attention.

The fundamental principles of Hydrostatics and Hydraulics might be familiarly illustrated by a va riety of simple experiments, some of which might be rendered extremely amusing. That fluids press in all directions-that their pressure is in proportion to their perpendicular height-that a small quantity of a fluid may be made to counterpoise any quantity, however great-that a fluid specifically lighter than another will float upon its surface-that the surface of all fluids which communicate with each other will be on the same level-that the velocity with which water spouts from holes in the side of a vessel, is in proportion to the square root of the distance of the holes below the surface of the water. These, and similar positions, along with the principles on which syphons, jets, and artificial fountains act, can be illustrated with an apparatus which every intelligent teacher, if he has the least share of mechanical ingenuity, can easily construct for himself, with the assistance of glass vessels, which are to be found in almost every family. To show that water will find its level, and rise to the same height in tubes which have a communication, an instrument similar to the following, Fig. 1. may be constructed: AB and ED are two tubes which have a communication with each other by means of the tube BD;