THE POET KLOPSTOCK TO THE NATIONAL ASSEMBLY OF FRANCE.

"Moderators of the French empire!

"I fend back to you with horror those titles of which I was fo proud, while I could think that they united me to a fociety of brothers and friends to humanity. Alas! the deception is but too foon vanished away, and most afflicting reality is come, to put an end to a delufive dream. Alas! I had vainly imagined, that from the diftant borders of the Seine that light fhould come, which would one day give an eclat to the happy reign of liberty amongst European nations.

66

Why have you deceived me? Your rights of man were only a fnare laid to make Frenchmen fall, that they might be the more easily affaffinated. Learn, then, that the excess of your barbarifm and of your crimes has placed an eternal barrier between you and the poets of happy Germany. When they are told thofe tragical adventures which difgrace your fanguinary history, they are affrighted and fly away. There is no connection now between us, you have broken for ever the last of the bands which connected us together.

"I pity thofe who call themfelves citizens, and who fhed torrents of the blood of citizens. O crime! when they have shed blood they dance around their victim; they contemplate with a dry eye the lait convulfion; they approach nearer to indulge their ears with the laft groan.

"Frenchmen, I turn away with affright from that impious troop which is guilty of affaffination, by looking on the peaceable witneffes of murder. I fly far off from the cries of that execrable tribunal which murders, not only the victim, but which murders also the merry of the people."

"

"Such is the energetic letter of the old and virtuous Klopstock; he had not attained the pitch of Condorcet and his companions, and they very probably confidered him as a fool and a dotard. This is not quite fo confoling as the addrefs of the English deputies with the 2000 pair of fhoes." P. 530.

We cannot dwell further upon the particulars of Mr. Playfair's hiftory: but willingly recommend it to those who are defirous of information concerning the arts as well as the crimes of the Jacobins. We obferve a fingular error in the argument prefixed to Chap. VI. and VII. (printed VIII. in the book by mistake) where the matter belonging to the end of the former, is placed as commencing the latter, as far as the words Martial Law. This error puzzled us once or twice in recurring to the matter of thofe parts, till we perceived how it was occafioned. The book is not in general incorrect,

ART.

ART. XVII. The Method of finding the Longitude at Sea by Time-keepers to which are added, Tables of Equations to Equal Altitudes, more extensive and accurate than any hitherto published. By William Wales, F. R. S. and Mafter of the Royal Mathematical School in Chrift's-Hofpital. 8vo. 115 pp. 2s. 6d. Wingrave. 1794.

WERE the longitude as cafily or as correctly afcertainable at fea as the latitude, the dangers of the navigator would be confiderably diminished; he could then exactly know the place of his thip, and confequently would be able to prepare against the evils of which his charts afforded warning. The method of finding it, therefore, becomes an object of greater importance to every community or ftate, as more of its members or fubjects are employed on the ocean. The English nation, when we confider the extent of its commerce, the greatnefs of its naval force, and the dangerous feas with which it is encompaffed, appears to be more interested in this matter than any other; and accordingly has offered, and actually given, greater rewards, for methods of determining the longitude at fea, than any other nation. Of the methods propofed for this purpose, which are of general ufe, there are two; one by the motion of the moon; the other by a watch, or timekeeper and of thefe, the former is brought much nearer to perfection than the latter.

The fubject of the pamphlet before us is, (as its title expreffes) the method of finding the longitude at fea by timekeepers; and as it comes from a perfon who holds a refpectable mathematical fituation, and who has had great experience in this bufinefs, having been employed by the Board of Longitude as astronomical obferver on board one of the ships which went round the globe, we fhall pay to it a more particular attention.

Mr. Wales begins with a brief, but clear defcription of the Terreftrial Globe, accompanied with a figure reprefenting fuch lines and circles of it as render the knowledge of what is meant by latitude and longitude easy to any capacity.

This being done, he next explains the difference between mean and apparent time, which is called the equation of time; and then shows how to find the quantity of it, at any inftant, and for any place on the earth, by means of the Nautical Almanac. This is his firft problem, for the folution of which he has given a general rule, and illuftrated it with several examples.

The fecond problem is, to find the fun's longitude for noon at any given place from the Nautical Almanac; the folution of

which is facilitated by a table of the fun's hourly motion. which he has inferted, together with feveral others, at the end of the pamphlet.

The third problem is, to find the fun's declination for any given time and place from the Nautical Almanac.

The fourth problem is, to find the mean time at any place, the latitude and longitude of that place, or the latitude, and time at Greenwich, being given.

For the folution of each of these problems a general rule is given, which is illuftrated by examples. The author then proceeds to explain the principles on which time-keepers are employed, which, though well known, we fhall infert in his words, as introductory to the fubfequent part, Having fhown how the longitude may be found at Greenwich, or the first meridian, he observes, that,

"If a watch, or time-keeper, be regulated to keep mean time, exactly, and be set to the mean time at the firft meridian, it is manifeft that fuch watch will continue to fhow the mean time at that meridian, as long as it continues to go at the fame rate, whatever place it may be carried to; and, confequently, if a watch fo regulated be kept on board a fhip, it will always fhow the mean time at the first meridian. Hence, if the mean time be found at the fhip, by the preceding problem, the difference between it and the time fhown by the watch, when the fun's altitude was obferved, being turned into degrees and minutes at the rate of 15° to an hour, will be the longitude of the place where the fun's altitude was observed.

It is not, however, abfolutely neceffary that the watch fhould either be fet precifely to mean time at the first meridian, or be regulated to keep exactly mean time; both of which might, perhaps, he difficult, or at least tedious to effect. The only thing which is abfolutely requifite in a watch, to render it equal to the task of finding the longitude is, that it will go uniformly at fome rate; because the rate which it does go at, as well as its deviation from mean tiine at the first meridian, may be readily found, (by the following problem】 and allowed for.

Strictly fpeaking, the rate of a watch is the number of hours, minutes, and feconds, which its hands appear to have moved over on the dial-plate in the space of a mean folar day; but it is customary to call the difference between this time and twenty-four hours the rate of the watch." P. 21.

This brings him to problem the fifth, to find the rate which a watch goes at; that is, how much it gains or lofes on mean time in a day, or twenty-four hours, and how much it is too faft, or too flow. for mean time at any place.

His first method of doing this is by obfervations of the altitude of the fun's lower limb, taken by Hadley's quadrant,

when

when the fun is at leaft four points of the compafs from the meridian. He fays, in p. 27,

"I have given this method of finding the rate which a watch goes at, because it may be put in practice by every feaman, without introducing the ufe of any inftrument or obfervation, which he is not already neceffarily acquainted with; and because it ada.its of being executed, if care and skill be exerted, with tolerable exactness; fufficient, at least, for the ufual length of a Weft-India voyage, out or home. It, however, requires a very good inftrument, and care and fkill in the use of it; moreover, the utmost exactness must be observed in the calculations; and, when the utmost skill in both is exerted, it is not fufficient for long voyages.

"The moft exact way of finding the rate which a watch goes at, and that which requires the least calculation, is the method practifed in fixed obfervatories, where they have tranfit inftruments adjusted to, and moving in the meridian of the place. This method has been lately adopted by fome gentlemen in the East-India Company's fervice, who have carried out portable tranfit inftruments, for the purpofe of examining their watches in India, before they fet out on their voyage home."

Mr. Wales then, in order to prepare his reader for understanding a fecond method of folving this problem, gives a defcription of the tranfit inftrument, its adjustments, and ufe. Four figures, reprefenting the whole infhument, and the feveral parts of it which are to be adjufted, are given on a copper-plate, which, together with his clear defcription, render the ufe of this inftrument eafy to be understood. The method of finding the rate at which a watch goes, by obfervations of the fun's tranfit over the meridian, taken with this inftrument, is then explained.

But this method of finding the rate of a watch, although it 'be very convenient in fixed obfervatories, on account of the cafe with which the obfervations are made, and the fimplicity of the calculations from them, yet, as he justly observes, in p. 63,

"Is not fo well adapted to the fkill and opportunities of feafaring men, in general, as fome others are; for it requires not only a confiderable degree of knowledge in practical aftronomy, but fome time alfo, to get a tranfit inftrument into the plane of the meridian. And, if the inftrument be not pretty exactly in the meridian, the obferver will not only get the abfolute quantity of time, which the watch is too faft, or too flow, wrong, but will, if there be any confiderablechange in the fun's declination while the watch is under trial, determine the rate of its going erroneously alfo."

He, therefore, propofes a third method of finding the rate of a watch, by obferving daily, or as often as opportunity. offers, the paffage of a fixed ftar over fome vertical circle,

with the tranfit inftrument, and noting the time by the watch. From thefe obfervations, the daily variations of the watch from mean time may very eafily be found, although the vertical plane in which the inftrument moves be at a distance from the meridian. The mean time, at the place of observation is to be found, by taking altitudes of the fun; and then it will alfo be known how much the watch is too fast, or too flow.

But, although it be not neceffary that the inftrument should be brought into the meridian, yet, as the author observes, it will be convenient to bring it as near to the meridian “as a well-defined mark can be found to adjuft it to." To this we add, that the times of the tranfits of two, or more, fixed stars, as fhown by the watch, may be noted as often as clouds do not interpofe; which will give the obferver a better chance for finding both the daily variations of the watch from mean time, and the whole of its gain or lofs in any propofed number of days, than can be had from attending to the paffages of one star only. We should alfo further recommend to the obferver, if the latitude he is in, and other circumstances admit of it, to choose fuch bright stars as have at least 20 degrees of meridian altitude, and not more than 30 degrees of declination.

We here (p. 65) meet with a finall mistake; the difference between a fidereal day and a mean folar day being taken in fidereal time instead of mean folar time, viz. 3'56,55 instead of 3' 55'91. This flip could not long efcape the ingenious writer of this pamphlet; and it was corrected with a pen in the copy that came to our hands. The reader, therefore, fhould infert 3'55",91, instead of 3'56",55, in pages 65, 66, and 67.

This method of folving the problem claims a preference, on account of faving time, both in feiting up the inftrument for use, and in the calculation.

A fourth method of finding the rate of a watch is by equal altitudes of the fun, obferved by Hadley's quadrant, of which he alfo gives a full and very clear defcription. The folution of the problem, by this method, is very much facilitated by tables which this author has calculated, and inferted at the end of the book, for correcting the inequality of the intervals between noon and the morning and afternoon obfervation, on account of the fun's change of declination in the time between these obfervations.

Of each of these methods of folving this 5th problem an example is given, which cannot fail to render the book still more ufeful and valuable to those who want information in this point.

The