and few priests could read their Breviary and Rituals fluently, -We cannot wonder at this in Iceland, when the hiftory of the church affords fo many examples of Bishops who were prefent at Councils, at the conclufion of which they caused to be written under the acts the following teftimony of their ignorance, "Quoniam dominus epifcopus fcribere nefcit, ideo ejus loco fubfcripfit N. N." i. e. Because my Lord the Bishop is unable to write, therefore N. N. fubfcribes his name for him. Dr. Von Troil pays a compliment to fome learned and ingenious gentlemen, natives of Iceland, who either refide in the country, or are travelling abroad in the laudable pursuit of knowledge. He places the prefent Bishop of Skalholt in the first class of Icelandic literati, and fpeaks of his Ecclefiaftical Hiftory as replete with information, criticifm, and erudition.' Our opinion of the merit of these letters may be collected from what we have before said. As to the tranflation (which is .probably the work of a foreigner), it is on the whole well performed: and though the conftruction in fome places is perplexed and inelegant, yet it is in general correct, and fufficiently intelligible. ART. VIII. An Account kept during thirteen Months in the Royal Obfer. vatory at Greenwich, of the going of a Pocket Chronometer; made on a new Construction, by John Arnold, having his new invented BaJance Spring, and a Compenfation for the Effects of Heat and Cold in the Balance. Published by Permiffion of the Board of Longitude. 4to. I s. 1780. Sold by John Arnold, No. 2, Adamflreet, Adelphi; alfo by T. Becket, Strand. REVIOUS to the account of the going of this excellent machine, which we fhall extract from the present pamphlet it may not be impertinent to give our Readers a fhort detail of what had been done by others, in the fame way, before the matter was taken up by Mr. Arnold. Gemma Frifius feems to have been the firft who fuggefted the method of finding the longitude at fea by means of watches, or time-keepers; which machines were then, as he fays, but lately invented. After him Metius, and fome others, attempted it; but the state of watch-making, as will cafily be imagined, was then too imperfect for this purpose. The difpute between Hooke and Huygens, concerning the invention and application of the pendulum fpring to watches, was long and violent: each of them claiming this curious and most useful invention, and reprefenting the other as a pirate. We fincerely believe that their claims were each of them juft, and confequently their accufations of each other equally unjuft: nor is this the only inftance in which different perfons have made the fame difcovery, nearly about the fame time. The geometrical conftruction of folar eclipfes by Flamfted, Halley, and Sir Christopher Wren; and and the invention of inftruments for taking angles at fea by reflection, by the late illuftrious Sir Ifaac Newton and Mr. Hadley, are now well known, and acknowledged to have been difcovered by the several perfons, intirely independent of each other. Moreover Hooke and Huygens, each of them, on making this discovery, applied it to the purpose of difcovering the longitude at fea. Some difputes, however, between the former of those gentlemen and the English miniftry, at that time, prevented the making any experiments with watches conftructed by him; but many experiments were made with watches conftructed by Mr. Huygens, from which it appeared that those watches were of no real use at fea, for this purpose. Dr. Hooke never, as far as we know, made a full difcovery of his inventions of this kind; but many hints are dropped, in different parts of the, Philofophical Tranfactions, his Philofophical Collections, and Cutlerian Lectures, of which later mechanics have undoubtedly availed themselves. In 1714, an act paffed for giving 20,000). "to that perfon who fhould firft difcover a method, by which a fhip might fail from England to any port in the Weft Indies, without having committed an error of 30' in her longitude, on arriving at the faid port. The firft who turned his thoughts this way, in confequence of this public encouragement, was Henry Sully, an Englishman, but who had left England before the paffing of this act for in 1714 he printed, at Vienna, a small tract on the fubject of watch-making; and foon after he removed from thence, and fettled at Paris, where he spent the remainder of his life in improving time-keepers for the difcovery of the longitude. In 1716 he prefented a watch, of his own making, to the Royal Academy of Sciences, which was much approved. It is particularly faid, that he had greatly diminished the friction; and that what he had not taken entirely away, he had, by a very fingular addrefs, rendered uniform. He went to Bourdeaux in 1726 for the convenience of trying his watches, and died there in 1728. The greater part of what is yet known of watchmaking in France is principally to be attributed to him; for the famous Julien le Roy was his pupil, and owed most of his inventions to him, which he afterwards perfected and executed; and this gentleman, his fon, and M. Berthoud, are the only perfons in France who have turned their thoughts this way fince the time of Sully. Several watches, made by the two latter artifts, have been tried at fea, at the expence of the King of France, and very voluminous accounts of these trials have been publifhed with great pomp; but the facts which are there related are fo very few, and thofe few enveloped in fuch a volume of words, vague and indeterminate in their meaning, that it is 0 4 fcarcely fcarcely poffible to discover, from thence, what these watches are capable of performing *, M. Berthoud, in a pretty bulky pamphlet in 4to, entitled Eclairciffemens fur l'invention, &c. des nouvelles machines proposées en France pour la determination des longitudes en Mer par la mesure du temps, has with great labour collected together a few of the principal facts which refulted from the three laft trials that were made of two time-keepers conftructed by M. Le Roy, marked A and S; and of two of his own construction, denominated No. 6 and No. 8, which are as follow: June 8th, 1768, being then at Havre de Grace, M. Le Roy's time-keeper A loft 1" a day on mean time; and S gained 4 a day. At the ifland Miquelon, on the coafts of Newfoundland, A was lofing at the rate of o" a day, and S gaining about 10" a day on mean time. At Cadiz S gained on different days between the 16th and 30th of September 1′′1⁄2, 1′′2, 3", 2", 3′′, 2′′ and 6" a day on mean time; and A gained on the fame days, refpectively, 2", 2", 3′′, 2, 53, 4′′, and 14" a day. A gained on mean time, at Breft, from the 4th of November to the 7th, at the rate of 7" in 24 hours, and S at the rate of 5′′ %. 7 In November 1768, the time-keepers, No. 6 and No. 8, made by M. Berthoud, were put to the trial in a voyage conducted by M. Fleurieu. Nov. 14th to Dec. 7th, at Rochford, (No. 8 lof No. 6 loft April 13th to 18th, at St. Jago, * See Journal du Voyage de M. le Marquis de Courtanvaux fur la Fregate L'Aurore pour effayer, par Ordre de l'Académie, plufieurs Inftruments relatifs à la Longitude. 4to, 1768. Voyage fait par Ordre du Roi en 1768, &c. par M. Caffini, fils, 1770. Voyage fait par Ordre du Roi, en 1768 & 1769, pour eprouver les Horloges Marines inventées par M. Ferdinand Berthoud, par Fleurieu, 4to. II. Tom. 1773. Voyage fait par Ordre du Roi en 1771 et 1772 pour verifier l'Utilité de plufieurs Methodes et Inftruments, fervant à determiner la Latitude et Ja Longitude. Par Meff. Verdun de la Crenne, Le Chevalier de Borda, et Pingrè, 4to. II. Tom. 1778. In the month of October 1771, two watches made by M. Le Roy, marked A and S, and M. Berthoud's No. 8, were again fent out on trial under Meff. Verdun, Borda, and Pingrè. A was the fame watch which had been tried before by the Marquis de Courtanvaux, and M. Caffini; but that marked S was a new one. They had alfo with them a fmall watch made by M. Le Roy, which, on account of its fize and form, they called La petite ronde: but this did not anfwer at all. The performances of the other three were as follow: At Breft, Oct. 10th to 26th, 177, Gain. 1739 Loft " 2 141 Gain. 1748 o 50 Do. I oc Do. 138 Do. o 19 Gain. o 44 Do. 263 Do. 1 46 Do. I 44 Do. Do. 1 11 Do. 2 66 Do. Do. 4 19 Do. 167 066 I 12 1 09 2 24 9 00 Do. Fort Royal, 17th to 26th Feb. Bref, 10th to 17th Oct. o 5o o 63 On the 17th of March the fhip ftruck on the Wilmington Rock, which lies off the island of Antigua; and the thermometer of compenfation for heat and cold of the watch A was broken by the fhock, and the watch put entirely out of order. This accident was the caufe of their putting back to Port Royal. Were we to form our judgement from this account, it would appear, that M. Berthoud's time-keepers greatly exceed thofe of M. Le Roy: but it ought, perhaps, to be obferved, that this (No. 8.) is the only one of his making which has performed fo well; and even this, on the former trial, did not go with any very great degree of regularity. About the year 1726, Mr. John Harrifon, whofe name is now fo well known on account of his time-keepers, began to apply himself to the conftruction of them: and in the year 1736, one of them was tried, on board his Majefty's fhips, in a voyage to and from Lisbon; in which trial it gave so much fatisfaction, that he received public encouragement to proceed, and began to entertain hopes of obtaining the reward offered by the act of the 12th of Queen Anne; in order to which, he made three other time-keepers, every one of which was more accurate, and better adapted to the purpose of measuring time truly at sea, than the former. The fecond of thefe was finished in 1739; and during the next ten years its going was fo much admired, by the ingenious men of thofe times, that the annual prize medal, diftri buted buted by the Royal Society, for improvements in experimental philofophy, was given to Mr. Harrifon on St. Andrew's day, 1749. Mr. Harrison did not finish his third machine until the year 1758; having then a fourth in confiderable forwardness, and which he finished in October 1761: this proved fo much to his fatisfaction, that he wrote immediately to the commiffioners of the board of longitude, informing them that he was then ready to make the ultimate trial prefcribed by the abovementioned act. Accordingly Mr. William Harrison, son of the inventor, embarked on board his Majefty's fhip Deptford, in November 1761, with this fourth time-keeper, on a voyage for Jamaica; and the longitude of the island, as fhewn by the timekeeper, on his arrival there, differed but one minute and a quarter of the equator from the true longitude deduced from Aftronomical Obfervations. The time-keeper alfo pointed out the longitudes of the feveral places, which they faw in the course of the voyage, in a very exact manner. Mr. Harrifon junior returned to England, with the time-keeper, in the latter end of March 1762, and found that it had erred in the whole, from its fetting out to its return to England, no more than 1′ 54′′ in time, or 28 minutes of longitude. Mr. Harrifon now claimed the whole reward of 20,000 1. offered by the act of the 12th of Queen Anne (1714); but fome doubts arifing in the minds of the Commiffioners concerning the true fituation of the ifland of Jamaica, the manner in which the time at that place had been found, as well as at Portsmouth; and it being further suggested by some, that although the timekeeper happened to be right at these two times, namely when at Jamaica, and on its return to England, it was by no means a proof that it had been always fo in the intermediate times, another trial was proposed in a voyage to the island of Barbadoes, in which precautions were taken to obviate as many of thofe objections as poffible. Accordingly, the Commiffioners having previously fent out proper perfons to make aftronomical obfervations at that ifland, which, when compared with other correfponding ones made in England, would determine, beyond a doubt, its true fituation; Mr. William Harrison again fet out, with his father's time-keeper, in the latter end of the month of March 1764, the watch having been compared with equal altitudes before he set out, at Portsmouth; and arrived at Barbadoes about the middle of May: where, on comparing it again with equal altitudes of the fun, it was found to fhew the difference of longitude between Portsmouth and Barbadoes 3h 55 3" the true difference of longitude between these places, refulting from aftronomical obfervations, is 3h 54′ 20′′: confequently the error of the watch was 43", or 10′ 45′′ of longitude. The watch gained at the rate of 2", 58 a-day on mean time, from |