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A letter from the learned Mr. Abraham Gronovius, se ceps, a quo aliquando Britannici regni majestas

cretary to the University of Leyden, Mr. Lauder, et populi salus pendebunt ! Interim tibi, erudiconcerning the A lamus Ersul vi Grotius.

tissime vir, atque etiam politissimo D. Caveo, Clarissirno Viro, Wilhelmo Laudero, Abru- pro muneribus literariis, quæ per nobilissimum hamus Gronovius, S. P. D.

Lawsonium f ad me curâstis, magno opere me Postquam binze literæ tuæ ad me perlatæ fue- obstrictum agnosco, eademque summa cum vorunt, duas editiones carminum H. Grotii, viri luptate a me perlecta sunt.

Filius meus te plurimùm salutat. vere summi, excussi; verùin ab utraque tragediam, quam Adanum Exsulem inscripsit ó távo, veum saluta, atque amare perge, Tuum.

Vale, doctissime vir, meisque verbis D. Ca abesse deprehendi; neque ullum ejusdem exemplar, quamvis tres* editiones exstare adnota: Dabam Leidis A. D. xiv. Kal. Maias,

ABRAHAMUM GRONOVIUM. veram, ullibi offendere potui, adeo ut spe, quam

A. D. MDCCXLVII. vorabam desiderio tuo satisfaciendi, me prorsus excidisse existimarem. Verùm nuperrime fortè contigit, ut primam!

POSTSCRIPT Tragedie Groliane editionem Hagæ, An. 1601, publicatam, beneficio amicissimi mihi viri nac- And now my character is placed above a.. ius fuerim, ejusque decem priores paginas, qui- suspi •ion of fraud by authentic documents, I bus præter chorum actus primus comprehenditur, will make bold at last to pull off the mask, and a Jacobo meo, optimæ spei adolescente, tran- declare sincerely the true motive that induced scriptas nunc ad te mitto. Vale vir doctissime, me to interpolate a few lines into scme of the meque ut facis amare perge. Dabam Lugd. authors quoted by me in my Essay on Milton, Bat. A. D. iv. Eid. Sept. A. D. MDCCXLVI. which was this: Knowing the prepossession in

favour of Milton, how deeply it was rooted in many, I was willing to make trial, if the partial

admirers of that author would admit a translation A second letter from the same gentleman to Mr. Lauder, of his own words to pass for his sense, or exhibit on the same subject.

his meaning; which I thought they would not: Clarissime atque Eruditissime Vir ! nor was I mistaken in my conjecture, forasmuch

as several gentlemen, scemingly persons of judgPosteaquam tandem Jacobus meus residuam ment and learning, assured me, they humbly partem, quam desiderabas, Tragædia Grolianæ conceived I had not proved my point, and that transcripserat, ut eâ diutius careres, committere Milton might have written as he has done supnolui : quod autem citius illam ad finem perdu- posing he had never seen these authors, or they cere von potuerit, obstiterunt variæ occupationes, had never existed. Such is the force of prejuquibus districtus fuit. Nam præter scholastica dice! This exactly confirms the judicious obser. studia, quibus strennè incubuit, ipsi componenda vation of the excellent moralist and poet: orat oratio, qua rudimenta linguæ Græcæ La

Pravo favore labi mortales solent, tinæque deponeret, eamque, quod vehementer

El pro judicio dum stant erroris sui, letor, venustè, et quidem stilo ligato, composuit, Ad pænitendum rebus manifestis agi. et in magna auditorum corona pronuntiavit. For had I designed (as the vindicator of Milton Quod autem ad exemplar ipsum, quo Adamus supposes) to impose a trick on the public, and Exsul comprehenditur, spectat, id lubens, si

procure credit to my assertions by an imposture, meum foret, ad te perferri curarem, verùm illud I would never have drawn lines from Hog's a clarissimo possessore tanti æstimatur, ut per- translation of Milton, a book common at every suasum habeam me istud minimè ab ipso impe- sale, I had almost said at every stall, nor ascribed traturum : et sanè sacra carmina Grotii adeò them to authors so easily attained : I would have rarò obvia sunt, ut eorundem examplar apud gone another way to work, by translating forty ipsos remonstrantium ecclesiastas frustra quæ- or fifty lines, and assigning them to an author, siveriin. Opus ipsum inscriptum est Henrico Bor the world expire at the general conflagration.

whose works possibly might not be found till BONIO, Principi Cond.£o; et forma libri est in My imposing therefore on the public in general, quarto, ut nullo pacto literis includi possit. Ce-instead of a few obstinate persons, (for whose terùin, pro splendidissima et Magnæ Britanniæ sake alone the stratagem was designed,) is the principe, cui meritò dicata est, digna editione only thing culpaple in my conduct, for which počtarum principis Johnstoni maximas tibi again I most humbly ask pardon : and that inus

and this only, was, as no other could be, my grates habet agitque Jacobus. Utinam illustris- design, no one I think can doubt, from the acsiinus Bensonus in usum serenissiıni principis, count i have just now given ; and whether that atque ingeniorum in altiora surgentium, eâdem formå jisdemque typis exarari juberet divinos shall leave every impartial mind to determine.

was so criminal, as it has been represented, I illos Ciceronis de Officiis libros, dignos sane, quos diurna nocturnaque manu versaret prin- The person here meant was the learned and worthy

Dr. Isaac Lawson, late physiciar: 'le English army ini Though Gronovius here mentions only three editions Flanders : by whom Mr. Gronovilla did me the honour of this noble and curious performance, the Adamus Ersul to transmit to me two of three acts of the Adamus Ersul or Grotius ; yet it appears from the catalogue of his works, of Grotius, transcribed by his son Mr. James. The truth that no fewer than four have been printed, two in quarto, of this particular consists perfectly well with the know and two in octavo, in the years 1601, 1609, and 1633; (woledge of the Doctor's in other John Lawson, Esq. coun having been made, one in quarto, the other octavo, Ánuo sellor at law; who are had the same thing lately cod 1801

firmed to him by Mr. Gronovius himself in Holland.





It is well known to seamen and philosophers, of the atmosphere, the effects of different effline that after the numerous improvements produced upon metals, the power of heat and cold upna by the extensive commerce of the later ages, the all matter, the changes of gravitation and ine great defect in the art of sailing is ignorance of hazard of concussion, I cannot but fear that they Longitude, or of the distance to which the ship will supply the world with another instance of has passed eastward or westward from any fruitless ingenuity, though I hope they will mi given meridian.

leave upon this country the reproach of unre. That navigation might at length be set free warded diligence. from this uncertainty, the legislative power of I saw therefore nothing on which I could fix this kingdom incited the industry of searchers with probability of success, but the magnetical into nature, by a large reward proposed to him needle, an instrument easily portable, and liide who should show a practicable method of find- subject to accidental injuries, with which the ing the longitude at sea; and proportionable sailor has had a long acquaintance, which he recompenses to those, who, though they should will willingly study, and can easily consult. not fully attain this great end, might yet make The magnetic needle from the year 1300, such advances and discoveries as should facili- when it is generally supposed to have been first tate the work to those that might succeed them. applied by John Goia, of Amalphi, to the sea

By the splendour of this golden encourage- man's use, seems to have been long thought to ment many eyes were dazzled, which nature point exactly to the north and south by the nanever intended to pry into her secrets. By the vigators of those times; who sailing commonly hope of sudden riches many understandings were on the calm Mediterranean, or making only set on work very little proportioned to their short voyages, had no need of very accurate ob strength, among whom whether mine shall be servations; and who, if they ever transiently numbered, must be left to the candour of pos- observed any deviations from the meridian, terity : for I, among others, laid aside the busi- either ascribed them to some extrinsic and acciness of my profession, to apply myself to the dental cause, or willingly neglected what it was study of the longitude, not indeed in expectation not necessary to understand. of the reward due to a complete discovery; yet But when the discovery of the new world not without hopes, that I might be considered turned the attention of mankind upon the naval as an assistant to some greater genius, and re- sciences, and long courses required greater ceive from the justice of my country the wages niceties of practice, the variation of the needle offered to an honest and not unsuccessful labourer soon became observable, and was recorded in in science.

-1500 by Sebastian Cabot, a Portuguese, who, at Considering the various means by which this the expense of the king of England, discovered important inquiry has been pursued, I found the northern coasts of America. that the observation of the eclipses, either of the As the next century was a time of naval adprimary or secondary planets, being possible but ventures, it might be expected that the variation at certain times, could be of no use to the sailor; once observed, should have been well studied : that the motions of the moon had been long yet it seems to have been little heeded; for it attended, however accurately, without any con- was supposed to be constant and always the sequence; that other astronomical observations same in the same place, till in 1625 Gellibrand were difficult and uncertain with every advan- noted its changes and published his observatage of situation, instruments, and knowledge: tions. and were therefore utterly impracticable to the From this time the philosophical world had a sailor, tost upon the water, ill provided with new subject of speculation, and the students of instruments, and not very skilful in their ap- magnetism employed their researches upon the plication.

gradual changes of the needle's direction, or the The hope of an accurate clock or time-keeper variations of the variation, which have hitherto is more specious. But when I began these stu- appeared so desultory and capricious, as to dies, no movements had yet been made that elude all the schemes which the most fancifal of were not evidently inaccurate and uncertain the philosophical dreamers could devise for its and even of the mechanical labours which I now explication. Any system that could have united hear so loudly celebrated, when I consider the these tormenting diversities, they seem inclined obstruction of movements by friction, the waste to have received, and would have contentedly of their parts by attrition, the various pressure numbered the revolutions of a central magne,

with very little concern about its existence, • An Account of an attempt to ascertain the Longitude could they have assigned it any motion, or vicis. at sen, hy an exact Theory of the

Vari-tion of the Mag. situde of motions, which could have correspond remarkable cities in Europe, from the year 1660 to 1969. ed with the changes of the needle. By Zachariah Williams.

Yet upon this secret property of magnetism I

ventured to build my hopes of ascertaining the Yet even this may be bome far better than the longitude at sea. I found it undeniably certain petulance of boys whom I have seen shoct up that the needle varies its direction in a course into philosophers by experiments which I have eastward or westward between any assignable long since made and neglected, and by improve parallels of latitude: and supposing nature to ments which I have so long transierred into be in this as in all other operations uniform and my ordinary practice, that I cannot remember consistent, I doubted not but the variation p!o- when I was without them. ceeded in some established method, though per

When Sir Isaac Newton had declined the office haps too abstruse and complicated for huinan assigned him, it was given to Mr. Molineux, one comprehension.

of the commissioners of the Admiraliy, who en This difficulty however was to be encoun-gaged in it with no great inclination to favour tered ; and by close and steady perseverance of me; but however thought that one of the instruattention I at last subdued, or thought myself ments, which, to confirm my owu opinion, and to have subdued, it; having formed a regular to confute Mi. Whiston's, I had exhibited io the system in which all the phenomena seemed 10 Admiralty, so curious or useful, that he surrepti

. be reconciled; and being able from the varia- tiously copied it on paper, and clandestinely tion in places where it is known to trace it to endeavoured to have it imitaied by a workman for those where it is unknown; or from the past to his own use. predict the future: and consequently knowing This treatment naturally produced remon the latitude and variation, to assign the true strances and altercations, which indeed did not longitude of any place.

continue long, for Mr. Molineux died soon after. With this system I came to London, where wards; and my proposals were for a time for • having laid my proposals before a nurober of gotten. ingenious gentlemen, it was agreed that during I will not however accuse him of designing to the time required to the completion of my condemn me, without a trial; for he demanded experiments, I should be supported by a joint a portion of my cables to be tried in a voyage subscription to be repaid out of the reward, 10 to America, which I then thought I had reason which they concluded me entitled. Among the to refusc him, not yet knowing how difficult it subscribers was Mr. Rowley, the memorable was to obtain, on any termis, an actual examiconstructor of the orrery; and among my fa- nation. Fourers was the Lord Piesley, a title not unknown About this time the theory of Dr. Halley was among magnetical philosophers. I frequently the chief subject of mathematical conversation; showed upon a globe of brass, experiments by and though I could not but consider him as too which my system was confirmed, at the house much a rival to be appealed to as a judge, yet of Mr. Rowley, where the learned and curious his reputation determined me to solicit his ac of that time generally assembled.

quaintance and hazard his opinion. I was At this time great expectations were raised by introduced to him by Mr. Lowthorp. and Dr. Mr. Whiston, of ascertaining the longitude by Desaguliers, and put my tables into his hands; the inclination of the needle, which he supposed which, after having had them about twenty days to increase or diminish regularly. With this under considera:ion, he returned in the presence learned man I had many conferences, in which of the learned Mr. Machin, and many other I endeavored to evince what he has at last con- skilful men, with an entreaty that I would publish fessed in the narrative of his life, the uncertainty them speedily; for I should do infinite serrice to and inefficacy of his method.

mankind. About the year 1729, my subscribers explained It is one of the melancholy pleasures of an my pretensions to the Lords of the Admiralty, old man, to recollect the kindness of friends, and the Lord Torrington declared my claim just whose kindness he shall experience no more. to the reward assigned in the last clause of the I have now none left to favour my studies; and act to those who should make discoveries con- therefore naturally turn my thoughts on those ducive to the perfection of the art of sailing by whom I was favoured in better days; and I This he pressed with so much warmth, that the hope the vanity of age may be forgiven, when commissioners agreed to lay my tables befivre I declare that I can boasi among my friends, Sir Isaac Newton, who excused himself, by almost every name of my time that is now rereason of his age, from a regular examination : membered: and that in that great period of but when he was informed that I held the varia- mathematical competition scarce any man failed tion at London to be still increasing, which he to appear as my defender, who did not appear as and the other philosophers, his pupils, thought my antagonist. to be then stationary, and on the point of re- By these friends I was encouraged to exhibit gression, he declared that he believed my system to the Royal Society, an ocular proof of the visionary. I did not much murmur to be for a reasonableness of my theory, by a sphere of time overborne by that mighty name, even when iron, on which a small compass moved in variI believed that the name only was against me: ous directions, exhibited no imperfect system of and I have lived till I am able to produce, in my magnetical attraction. The experiment was favour, the testimony of time, the inflexible shown by Mr. Hawkesbee, and the explanation enemy of false hypotheses; the only testimony with which it was accompanied, was read by which it becomes human understanding to op- Dr. Mortimer. I received the thanks of the pose to the authority of Newton.

society; and was solicited to reposit my theory My notions have indeed been since treated properly sealed and attested among their arwith equal superciliousness by those who have chives, for the information of posterity. I am not the same title to confidence of decision; men informed, that this whole transaction is recorded who, though perhaps very learned in their own in their minutes. studies, have had little acquaintance with mine. After this I withdrew from public notice,


and applied myself wholly to the con:inution |titude 50 40°; but that this is its true situation, of my experiments, the confirmation of my ! cannot be certain. The latitude of many places systein, and the completion of my tables, with is unknown, and the longitude is known of very no other companion than Mr. Gray, who shared few; and even those who are unacquainted wih all my studies and amusements, and used to re- science, will be convinced that it is not easily to pay my communications of magnetism, with his be found, when they are told how many degrees discoveries in electricity. Thus I proceeded Dr. Halley, and the French mathematicians, with incessant diligence; and perhaps in the place the Cape of Good Hope distant from each zeal of inquiry did not sufficiently reflect on other. the silent encroachments of time, or remember, Those who would pursue this inquiry with that no man is in more danger of doing little, philosophical nicety, must likewise procure bel• than he who fatters himself with abilities to do ier needles than those commonly in use. The all. When I was forced out of my retirement, needle, which after long experience I recomI came loaded with the infirmities of age, to mend to mariners, must be of pure steel, the struggle with the difficulties of a narrow fortune, spines and the cap of one piece, the whole length cut off by the blindness of my daughter from three inches, each spine containing four grains the only assistance which I ever had; deprived and a half of steel, and the cap thirteen grains by time of my patron and friends, a kind of and a half. stranger in a new world, where curiosity is now The common needles are so ill formed, or so diverted to other objects, and where, having no unskilfully suspended, that they are affected by merns of ingratiatiny my labours, I stand the many causes besides magnetism: and among single votary of an obsolete science, the scoff of other inconveniences have given occasion to the puny pupils of puny philosophers.

idle dream of a horary variation. In this state of dereliction and depression, I I doubt not but particular places may produce have bequeathed to posterity the following table ; exceptions to my system. There may be, in which, if time shull verify my conjectures, will many parts of the earth, bodies which obstruct show that the variation was once known; and or intercept the general influence of magnetism; that mankind had once within their reach an easy but those interruptions do not inf: inge the theo method of discovering the longitude.

ory. It is allowed, that water will run down will not however engage to maintain, that a declivity, though sometimes a strong wind all my numbers are theoretically and minutely may force it upwards. It is granted, that the exact; I have not endeavoured at such degrees sun gives light at noon, though in certain conof accuracy as only distracı inquiry without junctions it may suffer an eclipse. benefiting practice. The quantity of the varia- These causes, whatever they are, that intertion has been settled partly by instruments, and rupt the course of the magnetical powers, are partly by computation ; instruments musi al- least likely to be found in the great ocean, when ways partake of the imperfection of the eyes and the earth, with all its minerals, is secluded from hands of those that make, and of those that use the compass by the vast body of uniform water. them; and computation, till it has been recti- So that this method of finding the longitude, fied by experiment is always in danger of some with a happy contrariety to all others, is most omission in the premises, or some error in the easy and practicable at sea. deduction,

This method, therefore, I recommend to the It must be observed, in the use of this table, study and prosecution of the sailor and philothat though I name particular cities for the sake psopher; and the appendant specimen I exhibit of exciting attention, yet the tables are adjusted to the candid examination of the maritime naonly to longitude and latitude. Thus when I tions, as a specimen of a general table, showing predict that it Prague, the variation will in the the variation at all times and places for the whole year 1800 be 24 W. I intend to say, that it will revolution of the magnetic poles, which I have be such if Prague be, as I have placed it, after long

ago begun, and, with just encouragement, the best geographers, in longitude 14 30 E. la.) should have long ago completed.







may be demonstrated to excel in strength the SIR,

Dec. 1st, 1759.

elliptical arch, which approaching nearer to a

straight line, must be constructed with stones The Plans which have been offered by differ- whose diminution downwards is very little, and ent architects, of different reputation and abili- of which the pressure is almost perpendicular. ties, for the construction of the Bridge intended It has yet been sometimes asserted by hardy to be built at Blackfriars, are, by the rejection ignorance, that the elliptical arch is stronger than of the greater part, now reduced to a small num- the semicircular; or in other terms, that any ber; in which small number, three are supposed mass is more strongly supported the less it resis to be much superior to the rest; so that only upon the supporters. If ihe elliptical arch be three architects are now properly competitors for equally strong with the semicircular, that is, if an the honour of this great employment; by two of arch, by approaching to a straight line, loses tchom are proposed semicircular, and by the other none of its stability, it will follow, that all arcuelliptical arches.

ation is useless, and that the bridge may at last The question is, therefore, whether an ellipti- without any inconvenience, consist of stone laid cal or semicircular arch is to be preferred ? in straight lines from pillar to pillar. But if a

The first excellence of a bridge built for com- straight line will hear no weight, which is evimerce over a large river, is strength; for a bridge dent at the first view, it is plain likewise, that in which cannot stand, however beautiful, will boast ellipsis will bear very little; and that as ihe arch its beauty but a little while ; the stronger arch is is more curved, its strengih is increased. therefore to be preferred, and much more to be Having thus evinced the superior strength of preferred, if with greater strength it has greater the semicircular arch, we have sufficiently proved, beauty.

that it ought to be preferred; but to leave no obThose who are acquainted with the mathe-jection unprevented, we think it proper likewise matical principles of architecture, are not many; to observe, that the elliptical arch must always and yet lewer are they who will, upon any single appear to want elevation and dignity; and wat occasion, endure any laborious stretch of thought, it' beauty be to be determined by suffrages, the or harass their minds with unaccustomed inves- elliptical arch will have little to boast, since the tigations. We shall therefore attempt to show only bridge of that kind has now stood two bunthe weakness of the ellipticul arch, by arguments dred years without imitation. which appear simply to common reason, and If in opposition to these arguments, and in dewhich will yet stand the test of geometrical ex- fiance at once of right reason and general auamination.

thority, the elliptical arch should at last be chrsen, All arches have a certain degree of weakness. what will the world believe, than that some other No hollow building can be equally strony with a motive than reason influepced the determination? solid mass, of which every upper part presses And some degree of partiality cannot but be sus. perpendicularly upon the lower. Any weight pected by him, who has been told that one of the Jaid upon the top of an arch, has a tendency to judges appointed to decide this question, is Mr. force that top into the vacuity below; and the M-11-r, who having by ignorance, or thought. arch thus loaded on the top, stands only because lessness, already preferred the eliptical arch, will the stones that form it, being wider in the upper probably think himself obliged to maintain his than in the lower parts, that part that fills a own judgment, though his opinion will avail but wider space cannot fall through a space less liiele with the public, when it is known that Mr. wide; but the force which laid upon a flat would S-ps--n declares it to be false. press direcily downwards, is dispersed each way

He that in the list of the committee chosen for in a lateral direction, as the parts of a beam are the superintendency of the bridge, reads many puslıcd out to the right and left by a wedge driven of the most illustrious names of this great city, between them. In proportion as the stones are will hope thai the greater number will have more wider at the top than at the bottom, they can reverence for the opinion of posterity, than to lers easily be forced downwards, and as their disgrace themselves, and the inetropolis of the lateral surfaces tend more from the centre to each kingdom, in compliance with any man, who, ina side, lo so much more is the pressure directed stead of voting, aspires to dictué, perhaps witha laterally towards the piers, and so much less per out any claiin in such superiority, eiher by gicalpendicularly towards the vacuity.

ness of birih, dignity of employmen!, extent of Upun this plain prin.iple the semicircular arch I knowledge, or largeneas rif fortune.

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