LONGITUDE. 



tion, the fame ratio which twenty-four hours has to the in- 

 terval of time taken to defcribe that arc. 



It was ill the year 1714 that the parhament of Great 

 Britain firll begau to confider this queftioii as an objeft of 

 national concern. And the lofs of fir Cloudefly Shovel's 

 fleet feems to have had fome effeft in drawing their attention 

 to this fubject ; at leaft, if we may judge from the following 

 document, copied from a manufcript in the Royal Ob- 

 fervatory, figned by thofe well-known perfonages, William 

 Whifton and Humphrey Ditton. It appears to have been 

 one of the many petitions prefented to the houfe of com- 

 mons on tliis occafion. 



Reafons for a Bill, propofing a Reward for the Difcovery 

 of the Longitude. 



I. This bill is unexceptionable, becaufe it is general, and 

 not confined to any one projeft, perfon, or method;' but 

 gives equal hopes to all judicious propofers whatfoever. 



II. Becaufe in this bill no money is infilled on, before 

 any method for the difcovery of the longitude is, upon trial, 

 aftuaUy found practicable and ufeful. 



III. Becaufe fir Ifaac Newton's own paper, delivered 

 into the Committee, gives hopes that the known method by 

 the theory of the moon, which is hitherto not esaft enough, 

 may, upon due encouragement, in time be brought to per- 

 fection. 



IV. Becaufe the method now propofcd is owned by all, 

 to whom it has been communicated, to be certainly true in 

 theory : it cannot, therefore, be fit to have it concealed, even 

 though it were not yet known to be practicable ; becaufe, 

 in that cafe, future improvements might Hill make it fo. 



V. Becaufe its great ufe at land and in geography is in- 

 difputable, and was diftinclly obferved by fir Ifrac Newton 

 and Dr. Halley, upon the firft propofal of this method to 

 them : and we beg leave to fay, that this ufe alone \% fo great 

 and extenffue, that if there were no other, it would highly 

 deferve the encouragement of the public. 



VI. Becaufe another great ufe is alfo undoubted, vi%, 

 for all places in the narrow feas, and within about 1 00 miles 

 of all ftiores and iflands ; that is, for all places where fhips 

 are in the greateft danger, as fir Ifaac Newton owned to 

 the committee ; fo that if this method extended no farther, 

 yet it would highly deferve the public encouragement. 



VII. Becaufe there is little or no reafon to doubt of its 

 ufe at any place at fea, even where fliips are allowed to be 

 in the leaft danger ; fince, in the moft doubtful cafe ot all, 

 fir Ifaac Newton lias, in his paper delivered to the com- 

 mittee, propofed an cfFeAual remedy, as will be clearly un- 

 derftood, when the method itfelf is known to the world. 



VIII. Becaufe this method will fave the nation great 

 fums of money, which the want of it does now occafion, as 

 will appear upon trial. 



IX. Becaufe the charges of it will be inconfiderable, in com- 

 parifon of the advantage, as will alfo fully appear upon trial. 



X. Becaufe it will prevent the lofs of abundance of fhips 

 and lives of men ; as it would certainly have faved all fir 

 CloudeUy Shovel's fleet, had it then been put in practice. 



XL Becaufe it is eaiy to be underftood and pradtifed by 

 ordinary feamen, without the neceflity of any puzzling cal- 

 culations in aftronomy. 



And we take leave to recommend the learned Savihan 

 profeffor of geometry at Oxford, Dr. Halley, as the fittell 

 perfon in the world for the trial, and praftice, and improve- 

 ment of this method ; and do hereby declare, that we are 

 wilhng that he go equal (hares with us in the reward, if he 

 pleafe to imdertake lo ufeful a work, and the public pleafe 

 to make that reward equivalent to the great dignity and im- 

 portance of the difcovery. 



June ic, 1714. Will. Whiston. 



Hu.MPHKEY DlTTON. 



Accordingly an aft was pafled in this year, 17 14, in the 

 Britifii parliament, appointing and empowering certain com. 

 miffioners to make out a bill for a fum not exceeding 2000/. 

 towards making neceflary experiments ; and alfo granting a 

 reward to the perfon who fhould difcover the longitude at 

 fea, proportioned to the degree of accuracy that might be 

 attained by fuch method; ■viz. a reward of 10,000/., if it 

 determines the fame longitude to one degree of a great 

 circle, or fixty geographical miles; ij,ooo/., if it deter- 

 mines the fame to two-thirds of that diftance ; and 20,000/., 

 if it determines it to half that diftance. It is added, that 

 one moiety or half part of fuch rewards or fum ftiall be due 

 and paid when the faid commiflioners, or the major part of 

 them, do agree that any fuch method extends to the fecurity 

 of ftiips, within eighty geographical miles from the ftiores, 

 which are places of the greateft danger; and the other 

 moiety or half part, when a ftiip, by the appointment of the 

 faid coramiffioners, or the major part of them, fhall thereby 

 actually fail over the ocean, from Great Britain to any fuch 

 port in the Weft Indies as ihofe commiflioners, or the major 

 part of them, ftiall chufe or nominate for the experiment, 

 vvithout lofing her longitude beyond the limits above men- 

 tioned. 12 Ann. cap. 15. See alfa flat. 14 Geo. II. 

 cap. 39. 26 Geo. II. cap 25. By flat. 14 Geo. III. all 

 former atts concerning the longitude at fea are repealed, 

 except fo much of them as relates to the appointment and 

 authority of the commiflioners thereby conftituted, and alfo 

 fuch claufes as relate to the conftrudting, printing, pubhfti- 

 ing, &c. of nautical almanacs, and other ufeful tables ; 

 and it is enatted, that any perfon, who ftiall difcover any 

 method for finding the longitude by means of a time -keeper, 

 ftiall be entitled to the propofed reward, as we have already 

 ftated under the article Chronometer ; which lee. 



From the very confiderable improvements made by fir 

 Ifaac Newton in the theory of the moon, and more lately 

 by M. Euler, and others on his principles, Mr. Tobias 

 Mayer, profeffor of Gottingcn, was enabled to calculate 

 lunar tables more correft than any that were before pub- 

 liftied, and he has fucceeded fo far as to give the moon's 

 place within one minute of the truth. This has been proved 

 by a comparifon of the tables with the obfervations made 

 at the Greenwich obfervatory by the late Dr. Bradley, 

 and by Dr. Maftvelyne. Thefe ubles, for which the 

 widow of Mr. Mayer was rewarded by the Britilh parlia- 

 ment, were publiftied in 1770, by Dr. Mafkelyne, by order 

 of the cpmmiflioners of longitude. Dr. Malkelyne, in his 

 voyage to St. Helena, in 1761, made ufe of tliefe tables, 

 and found them to anfwer for the difcovery of the longitude, 

 within a degree ; and in order to facifitate the general ufe of 

 them, he propofed a nautical ephemeris, the fcheme of 

 which was adopted by the commiflioners of longitude, and 

 firft executed in the year J 767 ; and the pubUcation has been 

 regularly continued ever fince. But as the rules that were 

 given in the appendix to one of thofe publications, for cor- 

 recting the effects of refraction and parallax, were deemed 

 too difficult for general ufe, they were reduced to tables : 

 fo that by the help of the ephemeris, thefe tables, and others 

 that are provided, the calculations relating to the longitude, 

 which could not be performed by the moft expert mathe- 

 matician in lefs than four hours, may now be completed 

 with greater eafe and accuracy in half an hour. Dr. Maf- 

 kelyne obferved, that the error of Mr. Mayer's laft lunar 

 tables fcarce ever exceeds i' at the moft, and leldom amounts 

 to 20" ; and, therefore, the uncertainty hence arifing in the 

 determination of the longitude, can fcarcely exceed half a 

 degree, and generally will not exceed ten miles. 



We obferve, in general, with regard to the hiftorical part 

 of this article, that when Hadley had invented the quadrant, 

 or ottant, which ilill bears his name, and when Mayer liad 



brought 



