It will at once occur to you that as opinions can as easily be made habitual as cuftoms, it is a matter of great moment, to give an early habit of thinking rightly, and that this will more effectually be done by the general tenor of the converfations that pass in the hearing of children, than by any particular inftructions addrefs'd to themselves. Thus, for inftance, if they always hear cleanliness mentioned as a matter of effential confequence, finery with contempt, and those people spoken of as infignificant triflers who difcover any regard to the fhew of dress, they will infenfibly acquire a habit of efteeming cleanliness the only material part of their own drefs, without paying any fort of attention to the ornaments of it. I have feen the effect of this method in a child, who, at four years old, gravely cenfured the weakness of a perfon's judgment that had admired his new buckles. In the fame manner benevolence to mankind, compaffion toward the brute and infect creation, and every other good principle may be implanted in infancy, and infenfibly improved and ftrengthened in the mind, 'till right opinions are fo habitually rooted as to influence every part of the conduct through all future life; which is feldom, if ever, effected by formal precepts and grave inftructions. What children imbibe as by accident from the fentiments of others, always make a ftronger and more lafting impreffion than any lessons which appear to be intended peculiarly for themselves. This may, perhaps, be owing to the constrained attention required in the latter cafe, whereas in the former it is always voluntary, and, if not checked, will be conftant from their natural curiosity. This curiofity, properly managed, is the beft ground you can have to work upon, yet I have often with concern heard children fo feverely reprimanded for it as to make them afraid of feeming to hear the converfations that paffed in their presence : on the contrary, not the least notice fhould apparently be taken of their attention, while every thing faid before them should be regulated by the expectation of it. On this account chiefly the bringing them into mix'd company is injurious, as the contrariety of opinions will be apt to confuse their minds, which, to be advantageously form'd, must be used to a perfect sameness of fentiment in all whom they converfe with, or are attended by. Here alfo the great difficulty is to meet with fervants who will minutely obferve every direction given them, which is a point of fo much confequence as to deserve the utmost care. You will here fee the neceffity of extending your instructions to them even to the moft trifling circumftances, that nothing may be left to their own judgment, which can never be depended on and that thofe fervants who particularly belong to the nurfery should only be admitted into it, nor on any occafion others

be

be allowed to converse with them there, for reasons too obvious to need repeating.

The impropriety of one custom may not, perhaps, from its being fo general, occur to you with all the ftrength it deferves; I mean that of promifing wives and husbands as a dif tant reward for the good behaviour of children; to which may be added the no lefs abfurd practice of teaching them to give each other that appellation almost as soon as they can speak. I believe, my dear Louifa, you need only reflect seriously upon the effect this must neceffarily have on their young minds, and on the confequences that may naturally be fuppofed to follow from it, to suggest to yourself all I could fay on the fubject. Your judgment is fufficient to direct you in all the new relations you are entering upon, and your invariable inclination to dif charge your duty will fecure a conftant attention to the dictates of it; nor have I the leaft doubt of your fetting an example, in every respect, worthy of imitation, and consequently of your enjoying through life as great a fhare of happiness as this imperfect state can admit of, to be encreafed only by that unalterable felicity beyond the grave, which must be the reward of virtues like your's.-This opinion continually affords the fincereft pleasure to

Your affectionate, &c.'

The adventures of Alphonfo are intended to enforce an opinion, that mankind are under the protection of a fuperior order of beings, by whom, if it is not their own fault, they will be guarded from all real evil. In this story some characters are introduced, which feem to be taken from the life.

XI. Tables and Tracts relative to several Arts and Sciences. By · James Ferguson, F. R. S. 8vo. Pr. 45.

TH

Cadell.

HE science of aftronomy has at all times received additional improvement by the help of tables and inftruments properly calculated and conftructed for determining the places, motions, and other phænomena of the planets, both primary and fecondary. The oldest tables of this fort are the Ptolemaic, found in Ptolemy's Almageft, and were, so long fince as 1252, corrected by Alphonfo XI. king of Caftile, and thence called the Alphonfine tables.

The invention of fuch machines or inftruments as are now called Orreries and Planetariums, is alfo of an early date. The. first we have any mention of is that of Archimedes, generally called Archimedes's fphere. This famous machine was of a very complex nature, and confifted of a sphere, not of circles,

Ff4

but

but of an hollow globular furface of glass, within which was a piece of mechanism to exhibit the motions of the moon, the fun, and the five planets. The next orrery we find mentioned is that of Pofidonius the Stoic, in Cicero's time, eighty years before the birth of Chrift; and of which that illuftrious orator fays, "If any man should carry this fphere of Pofidonius into Scythia or Britain, in every revolution of which the motions of the fun, moon, and five planets, were the fame as in the heavens each day and night, who in those barbarous countries could doubt of its being finished (not to fay actuated) by perfect reafon ?" What would. Cicero fay, were he now to rife from the grave, and see his barbarous Britain abounding in or reries of various kinds and fizes, with all the improvements they have received fince the age in which he lived!

The moft confiderable articles in this performance are the tables and precepts for calculating the true time of new and full moon in any given year and month, from the creation of the world till the 6000th year after the end of the present century; and the description of fome new and useful improvements which our author has made in the feveral kinds of orreries for explaining the ufual phænomena of the celeftial motions thefe, in our opinion, are executed in a very judicious and careful manner.-Mr. Ferguson's method of facilitating the learner's conception of the motions of the planetary system being rather uncommon, we fhall take the liberty to transcribe the following as a specimen of it. The dome of St. Paul's is 145 feet in diameter. Suppofe a globe of this size to reprefent the fun; then, a globe of 97% inches will reprefent Mercury; one of 17 inches, Venus; one of 18 inches, the Earth; one of 5 inches diameter the Moon (whose distance from the earth is 240,000 miles); one of 10 inches, Mars; one of 15 feet, Jupiter; and one of 11 feet, Saturn, with his ring four feer broad, and at the fame diftance from his body all around.

In this proportion, suppose the fun to be at St. Paul's ; then Mercury might be at the Tower of London; Venus at St. James's palace; the Earth at Marybone; Mars at Kensington; Jupiter at Hampton-Court, and Saturn at Cliefden: all moving round the cupola of St. Paul's as their common center."

With regard to placing of fun-dials, p. 73. I muft, continues our author, make an observation, that may, perhaps, feem a very odd one to most people, which is, that if the dial be made according to the ftrict rules of calculation, and be truly fet at the inftant when the funs is on the meridian; it will be a minute too faft in the forenoon, and a minute too flow in the afternoon, by the fhadow of the ftile; for the edge of the fhadow that fhews the time is even with the fun's fore

moft

with his hind

But it is the

moft edge all the time before noon, and even moft edge all the afternoon, on the dial. fun's center that determines the time in the (fupposed) hourcircles of the heaven. And as the fun is half a degree in breadth, he takes two minutes to move through a space equal to his breadth; fo that there will be two minutes at noon in which the fhadow will have no motion at all on the dial. Confequently, if the dial be fet true by the fun in the forenoon, it will be two minutes too flow in the afternoon; and if it be fet true in the afternoon, it will be two minutes too faft in the foreThe only way that I know of to remedy this, is to fet every hour and minute division on the dial one minute nearer XII. than the calculation makes it to be." How it is poffible that Mr. Ferguson, who, in other cafes, has given many instances of his mathematical understanding, fhould fo totally want it in this, is difficult to ascertain. Surely that gentleman could never imagine the fhadow of a gnomon to be at reft while the fun itself was in motion; and to suppose the fun without motion for the space of two minutes near the time of noon, is too abfurd to merit a refutation.

noon.

In the remaining parts of this treatise, the author has interfperfed feveral curious and interesting particulars relating to the various branches of mixed mathematics, which cannot fail of being useful to the diligent reader; and, notwithstanding the mistake abovementioned, (the only one of consequence in the whole performance) we will venture to pronounce it a work of very confiderable merit.

XII. The Nautical Almanac and Aftronomical Ephemeris, for the Year 1767. Publifhed by Order of the Commiffioners of Longi8-30. 65. Nourse.

tude.

WE

E are given to understand in the preface to this very extraordinary performance, that at the defire of the commiffioners of Longitude, the Rev. Nevil Maskeline, Astrononomer-Royal, drew up the explanation and ufe of the articles contained in the Nautical Ephemeris, and the inftructions, with examples, for finding the longitude at sea, by help of the fame; that he alfo collected and calculated the fixteen first pages of tables requifite to be ufed with the Ephemeris; computed the table of proportional logarithms, which alfo feemed to him abfolutely neceffary to clear this method of any remaining difficulty; and likewife added explanations of all the tables, and a correction which may, he fays, be applied by the curious to the effect of refraction on the moon's diftance from a ftar, found by Mr. Lyons, or any

other

other method, on account of the barometer and thermometer. This reminds us of a scheme which a very ingenious perfon (lately dead) propofed fome few years ago, for ascertaining the moft advantageous times, depending upon the different preffures of the atmosphere, for purchafing diamonds, and fuch other jewels, as are usually fold by weight; but as the principles upon which his calculations were founded, seemed to tend rather towards raifing the height of filver in his own pocket, than affecting that in the tube of the barometer, the defign met with no encouragement,

With regard to the utility of the work before us as an aftronomical ephemeris for facilitating the calculations to be used in determining the longitude at sea, by an obfervation of the apparent diftance of the moon from the fun or a fixed star, we think it will prove of very little service to mariners, on account of the difficulty and prodigious labour attending the operations required to produce the neceffary corrections; not to mention the confused and almost unintelligible method in which they are defcribed. But granting it were otherwife, what advantage could be gained, after all these tedious and operofe calculations were made, to obtain the correction of perhaps only a few seconds, when, at the fame time, the very method of taking the distances as abovementioned is, in our opinion, fubject to much greater variation, (upon an optical account) according to the different latitudes in which the observer shall happen to be fituated, than all the corrections obtained by the ephemeris put together can poffibly compenfate?

We apprehend our readers will be able to form an exact judgment of the merit of the Nautical Ephemeris by the following extracts.

To find the effect of refraction and parallax.

In Table I. find what number answers to the two altitudes of the moon and ftar, the leffer of the two altitudes being found at the top of the table, the other in the first column on the left hand.

• Prefix the index 2 to this number (confidered as the decimal part of a logarithm) and add it to the logarithmic cofecant of the apparent distance of the moon and ftar, and abating 10 from the index of the fum, find what natural number answers to it in the table of logarithms.

From this number fubtract that correfponding to the given diftance, and to the leffer of the two altitudes in Table II. if the distance is less than 90°, or add them together if the diftance exceeds 90°; the remainder or fum is the effect of refraction in feconds; which added to the observed distance, gives the diftance cleared of refraction.