Imatges de pàgina

It will at once occur to you that as opinions can as easily be made habitual as customs, it is a matter of great moment, to give an early habit of thinking rightly, and that this will more effetually be done by the general tenor of the conversations that pass in the hearing of children, than by any particular inítructions address'd to themselves. Thus, for instance, if they always hear cleanliness mentioned as a matter of essential consequence, finery with contempt, and those people fpoken of as insignificant triflers who discover any regard to the shew of dress, they will insensibly acquire a habit of esteeming cleanliness the only material part of their own dress, 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 censured the weakness of a person's judgment that had adınited his new buckles. In the same manner benevolence to mankind, compassion toward the brute and infect creation, and every other good principle may be implanted in infancy, and insensibly inproved and strengthened in the mind, 'till right opinions are fo habitually rooted as to influence every part of the conduct through all future life; which is seldom, if ever, effected by formal precepts and

grave instructions. What children imbibe as by accident from the sentiments of others, always make a stronger and more lasting impreflion than any lessons which appear to be intended peculiarly for themselves. This may, perhaps, be owing to the constrained attention required in the latter case, whereas in the former it is always voluntary, and, if not checked, will be constant from their natural curiosity. This curiofity, properly managed, is the best ground you can have to work upon, yet I have often with concern heard children fo severely reprimanded for it as to make them afraid of seeming to hear the conversations that paffed in their presence : on the contrary, not the least notice should apparently be taken of their attention, while every thing said 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 perfe& sameness of sentiment in all whom they converse with, or are attended by. Here also the great difficulty is to meet with servants who will minutely observe every dire&tion given them, which is a point of so much consequence as to deserve the utmost care. You will here see the necessity of extending your instructions to them even to the most trifling circumstances, that nothing may be left to their own judgment, which can never be depended on ; and that those servants who particularly belong to the nur, sery should only be admitted into it, nor on any occafion others


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

· The iimpropriety of one custom may not, perhaps, from its being so general, occur to you with all the strength it deferves ; I inean that of proinising wives and husbands as a diftant reward for the good behaviour of children; to which may. be added the no less absurd practice of teaching them to give each other that appellation almost as soon as they can speak. I believe, my dear Louisa, you need only reflect seriously upon the effect this must necessarily 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 say on the subject. Your judgment is sufficient to direct you in all the new relations. you are entering upon, and your invariable inclination to difcharge your duty will fecure a constant attention to the dictates of it; nor have I the least doubt of your setting an example, in every respect, worthy of imitation, and consequently of your enjoying through life as great a share of happiness as this imperfect state can admit of, to be encreased only by that unalterable felicity beyond the grave, which must be the reward of virtues like your's.—This opinion continually affords the fins cereft pleasure to

• Your affectionate, &c.' The adventures of Alphonso are intended to enforce an opis nion, that mankind are under the protection of a superior order ot' 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 seem to be taken from the life.


XI. Tables and Tracts relative to several Arts and Sciences. By

James Ferguson, F.R. S. 8vo. Pr. 4s. Cadell.
HE science of astronomy has at all times received addi-

tional improvement by the help of tables and instruments properly calculated and constru&ed for determining the places, motions, and other phænomena of the planets, both primary and secondary. The oldest tables of this sort are the Ptolemaic, found in Ptolemy's Almagelt, and were, so long Unce as 1252, corrected by Alphonso XI. king of Castile, and thence called the Alphonfine tables.

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



but of an hollow globular surface of glass, within which was a piece of mechanisın to exhibit the motions of the moon, the sun, and the five planets. The next orrery we find mentioned is that of Posidonius the Stoic, in Cicero's time, eighty years before the birth of Chrift; and of which that illustrious orator says, " If any man should carry this sphere of Posidonius into Scythia or Britain, in every revolution of which the motions of the fun, moon, and five planets, were the same as in the heavens each day and night, who in those barbarous countries could doubt of its being finished (not to say actuated) by perfect reason?” What would. Cicero say, were he now to rise from the grave, and see his barbarous Britain abounding in orreries of various kinds and fizes, with all the improvements they have received since the age in which he lived !

The most 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 boooth year after the end of the present century; and the description of fome new and useful improvements which our author has made in the several kinds of orreries for explaining the usual phænomena of the celestial motions : these, 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 shall take the liberty to transcribe the following as a specimen of it. • The dome of St. Paul's is 145

feet in diameter. Suppose a globe of this fize to represent the fun; then, a globe of 976 inches will represent 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 n feet, Saturn, with his ring four feet broad, and at the same distance 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 must, 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 strict rules of calculation, and be truly fet at the inftant when the suns is on the meridian ; it will be a mi. nute too fast in the forenoon, and a minute too flow in the afternoon, by the shadow of the stile ; for the edge of the Madow that shews the time is even with the fun's fore


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most edge all the time before noon, and even with his hindmost edge all the afternoon, on the dial. But it is the fun's center that determines the time in the (supposed) houre circles of the heaven. And as the sun 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 shadow will have no motion at all on the dial. Consequently, if the dial be set true by the sun in the forenoon, it will be two minutes too Now in the afternoon; and if it be set true in the afternoon, it will be two minutes too fast in the fore

The only way that I know of to remedy this, is to set every hour and minute division on the dial one minute nearer XII. than the calculation makes it to be.” How it is possible that Mr. Ferguson, who, in other cases, has given many instances of his mathematical understanding, should fo totally want it in this, is difficult to ascertain. Surely that gentleman could never imagine the shadow of a gnomon to be at rest while the sun itself was in motion ; and to suppose the sun without motion for the space of two minutes near the time of noon, is too absurd to merit a refutation.

In the remaining parts of this treatise, the author has interspersed several 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 considerable merit.



XII. The Nautical Almanac and Apronomical Ephemeris, for the

Year 1767. Published by Order of the Commiffioners of Longitude. 830. 6s. Nourse. E are given to understand in the preface to this very ex

traordinary performance, that at the desire of the missioners of Longitude, the Rev. Nevil Maskeline, Astrononomer-Royal, drew up the explanation and use of the articles contained in the Nautical Ephemeris, and the instructions, with examples, for finding the longitude at sea, by help of the same; that he also collected and calculated the fixteen first pages of tables requisite to be used with the Ephemeris ; computed the table of proportional logarithms, which also seemed to him absolutely necessary to clear this method of any remaining difficulty; and likewise added explanations of all the tables, and a correction which may, he says, be applied by the curious to the effect of refraction on the moon's distance from a ftar, found by Mr. Lyons, or any


other method, on account of the barometer and thermometer. This reminds us of a scheme which a very ingenious person (lately dead) proposed some few years ago, for ascertaining the most advantageous times, depending upon the different pressures of the atmosphere, for purchasing diamonds, and such other jewels, as are usually sold by weight; but as the principles upon which his 'calculations were founded, seemed to tend rather towards raising the height of silver in his own pocket, than affecting that in the tube of the barometer, the design met with no encouragement,

With regard to the utility of the work before us as an astronomical ephemeris for facilitating the calculations to be used in determining the longitude at sea, by an observation of the apparent distance of the moon from the sun 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 described. But granting it were otherwise, what advantage could be gained, after all these tedious and operose calculations were made, to obtain the correction of perhaps only a few seconds, when, at the same time, the very method of taking the distances as abovementioned is, in our opinion, subject to much greater variation, (upon an optical account) according to the different latitudes in which the observer fall happen to be situated, than all the corrections obtained by the ephemeris put together can possibly compensate?

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 star, the lesser 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 (considered as the decimal part of a logarithm) and add it to the logarithmic cosecant of the apparent distance of the moon and star, and abating 10 from the index of the sum, find what natural number answers to it in the table of logarithms.

• From this number subtract that corresponding to the given distance, and to the leffer of the two altitudes in Table II. if the distance is less than 90°, or add them together if the distance exceeds 90°; the remainder or sum is the effect of refraction in seconds; which added to the observed distance, gives the distance cleared of refraction,

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