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thod offered by Mr Hardy, in the pamphlet before us; which is by the appulses of the moon to the meridian of the place. In order to this, he lays down the following proposition : • The right ascension of the sun when he is upon one meridian differs from his right ascension when upon another meridian: and this difference is to the horary difference of those meridians, as the increase of the sun's right alcenfion in 24 hours to the space run over by a meridian in the same time.'
From this proposition he deduces the following lemma: č Although when the sun comes to the meridian of any place, it is always 12 o'clock at that place, and so no horary difference can be discovered merely by observing the time of his appulse to different meridians; yet the moon comes not to all meridians at the same time, but at times differing from one another in proportion to the velocity of the moon in her orbit, and the distance of those meridians from each other.
This seems to have been but little attended to; yet every astronomer will assent to it as soon as it comes to be explained. Let us fix upon London for one meridian, and let us fuppose another distant from it 28 degrees weftward. This converted into time=1 hour 52 minutes. The moon is continually shifting eastward : suppose then that the moves at this time 15 degrees in 24 hours ; that is, i degree 10 minutes in 1 hour 52 minutes, Suppose then, that the moon is observed to be upon the meridian of Londoni at 12 o'clock, P. M. it is now at our meridian 10 hours 8 minutes, P. M. But by that time it is twelveo'clock P.M. at this latter meridian, the moon will be eastward from it idegree 10 minutes. And therefore, this meridian must go fo much farther eastward before it will pass through the moon; that is, it will be 12 hours 4 minutes 40 seconds at this meridian when the moon is upon it. Now the faster or flower the moon moves, the later or sooner will this meridian overtake her; and the farther any meridian is distant from this, eastward or westward, the sooner or later' will that meridian arrive at the moon; which is what we proposed in our lemma.
• From whence we may deduce an easy method for dilcovering the longitude of a ship at sea, supposing the moon's theory to be known. For then we can certainly calculate the time of the moon's appulse to each meridian, and make proper tables of such her motion. Suppose we then,
that we have a table shewing at what time the moon comes to the meridian of London each night in the year. We have also a table for the moon's hourly motion, and so for any smaller time; confequently, we have the difference of time between the appulse of the moon to the meridian of London and a meridian i degree eastward and westward. Let us then suppose every thing as in the preceding lemma: in this case for every degree of longitude we are to allow 10 seconds. Suppose then I was at sea, and by observation I found that the moon was upon the meridian of the ship at 11 o'clock, P. M. By the tables just mentioned, I found, that the moon came to the meridian of London this same night, at 10 hours 55 minutes 20 seconds, P. M. The difference of time then' is 4 minutes 40 seconds=280 seconds; which divided by ten seconds, the quotient will be 28 degrees, which is my true distance westward from London.
· Thus it appears that this method is true in theory : but I am aware that it will be objected, that the theory of the moon is not perfect enough for our purpose. Her inequalities are not suficiently known, so as to calculate her true place nearer than two or three minutes of a degree: and if her true place cannot be determined, then, neither can the true time of her appulse to any particular meridian be determined.
• But this is no objection to our present method ; for the error of appulse will always be in proportion to the error of her place : and in the same proportion will be the difference of time between her appulse at the meridian of London, and a meridian distant from thence degree eastward and westward; while the time of appulse to the meridian of the ship is had from immediate observation; and so has no dependance on the aforesaid calcutions. Though therefore the time of her appulse to the meridian of London and the meridian of the ship be greater or less than it should be; yet because the number by which that time is to be divided is always greater or less than it should, in the same proportion as that time is greater or less than it should be, the quotient will still be the same; and this quotient is no other than the difference of longitude in degrees. All this is very clear from the doctrine of proportion : for, if the divisor and the dividend be diminished in the same proportion, the quotient will still be the fame.'
The author then proceeds to shew how to correct any errors in the longitude by observing the culmination of a
ftar. And also how to multiply the opportunites of difcovering the longitude, by shewing how it may be found by an observation of the moon in any other situation.
But the principal thing which at present seems wanting to render this and the former methods practicable at sea, is a true knowledge of the hour of the day or night, when any obfervation is made. And with regard to Mr. Hardy's method, the chief difficulty is to find the exact time of the moon's appulse to the meridian, which by the methods at present in use at sea, seems almost impoffible. It is well known to those who have made observations upon the sea, how difficult it is to obtain the altitude of the sun to two or three minutes, even by that noble instrument lately invented by the learned Mr. Hadley; and consequently the appulse of the sun or other object to the meridian, can hardly be obtained so near as one minute, which will produce a prodigious error in the longitude. Indeed, upon the land, by the help of good instruments, especially by a mural arch, the time of appulfe may be found to the greateft exactness; but this is not the case at sea; the mariner is exposed to unavoidable errors in his observations, which flow from different quarters ; especially from the prodigious motion of the ship.
But it is well known, that if a method ever so easy were proposed for finding the longitude at sea, it could not be put in practice, with any desireable success, till the longitudes of the sea-coafts were better determined; for it is very certain, that the furer any man is of the longitude of any place at sea, the surer he is to miss the port he is designed for if the longitude of that place be not truly determined ; and therefore, the first thing neceffary to be done, is to have all our sea-coafts better settled, and new fea charts form’d: let this be first executed, and the fuccess of these observations will doubtlefs encourage them to put these methods in practice at fea; for things which we are unacquainted with, generally seem more difficult than they really are, and experience often renders those things easy, which at first sight we thought impossible.
ART. XIX, HERMES ; or, A Philosophical Inquiry cona
cerning Language and Universal Grammar. By James Harris. 8vo. 6s. Nourse and Vaillant.
HE subject of the performance now before uś, how
useful soever, is, at best, but dry and unentertains ing, and cannot easily be handled in such a manner as to be agreeable to the generality of readers. Our learned and ingenious author, however, has treated it with great accuracy and precision, and shewn a thorough acquaintance with the best ancient grammarians and philosophers, from whose writings he has filled his book with a multiplicity of quotations. He has not confined himself entirely to what is promised in the title-page of his work, but has expatiated freely into whatever is collateral, aiming, as he tells us in his preface, on every occasion to rise in his enquiries, and to pass, as far as possible, from small matters to the greatest.
The whole work is divided into three books in the two first of which language is refolv’d, as a whole, into its conftituent Parts. Our author begins from a period or sentence; which, after Aristotle, he calls a compound quantity of sound fignificant, of which certain parts are themselves also signifia cant. All the different species of sentences he reduces to two clasles, viz. sentences of assertion, and sentences of volitionz referring them to the two leading powers of the soul, perception and volition. After this he proceeds to treat of words, the smallest parts of speech. Now these, he tells us, are all either significant by themselves, or fignificant by relation: if significant from themselves, they are either substantives or attributives ; -if significant by relation, they are either definitives or conne&tives. So that, under one of these four species, substantives, attributives, definitives and connectives, or, in other terms; nouns, verbs, articles and conjundions, he includes all words however different.
Having reduced all words to these four classes, he goes 'on to give each of them a distinct and separate consideration, and begins with substantives, which, he tells us, are either primary or secondary, that is to say in a more familiar language, nouns or pronouns. The nouns denote subftances, and those either natural, as man, oak, &c. artificial, as house, fhip, &c. or abstract, as motion, virtuez &c. They inoreover denote things either generals or special, or particular. The pronouns, their substitutes, are Vol. VI.
either prepositive or subjunctive, The prepositive is distinguished into three orders, called the first, the second, and the third person. The subjunetive, (who, which, that) includes the powers of all those three, having superaddéd, as of its own, the peculiar force of a connective.
Having done with substantives he proceeds to attributives, which he divides into those of the firft, and those of the fecond order. Verbs, participles, and adjectives, as denoting the attributes of substances, he calls attributives of the first order; and adverbs he calls attributives of the second order, as denoting attributes of attributes. He treats fully and distinctly of the various ipecies and attributes of verbs, and bestows a long chapter on time and tenses, which being a curious subject, we ihall present our readers with the greatest part of what he says upon it, as a specimen whereby they may, in fome measure, judge of the rest of his performance.
“Time and Space, says he, have this in common, that they are both of them by nature things continuous, and as such they both of them imply extension. Thus between London and Salisbury there is the extension of space, and between yesterday and to-morrow, the extension of time. But in this they differ, that all the parts of space exist at once and togethering while those of time only exist in transition or fucceffion. Hence then we may gain some idea of time, by considering it under the notion of a transient continuity. Hence allo, as far as the affections and properties of transition go, time is different from space ; but as to those of extension and continuity, they perfectly coincide.
· Let us take, for example, such a part of space, as a line. In every given line we may assume any where a point, and therefore in every given line there may be affumed infinite points. So in every given time we may affume
any where a now or Instant, and therefore in every given time there may be assumed infinite nows or inftants,
i Farther still-A Point is the bound of every finite line; and a Now or Instant, of every finite time. But although they are bounds, they are neither of them parts, neither the point of any line, nor the now or instant of any time. If this appear strange, we may remember, that the parts of any thing extended are necessarily extended also, it being efa sential to their character, that they should measure their whole. But if a Point or Now were extended, each of them would contain within itself infinite other Points, and infinite other Nows (for these may be assumed infinitely within the minuteft extenfion) and this, 'tis evident, would be absurd and impossible,