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And now my character is placed above all suspicion of fraud by authentic documents, I will make bold at last to pull off the mask, and declare sincerely the true motive that induced me to interpolate a few lines into some of the authors quoted by me in my Essay on Milton, 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 of his own words to pass for his sense, or exhibit his meaning: which I thought they would not: nor was I mistaken in my conjecture, forasmuch as several gentlemen, seemingly persons of judgment and learning, assured me, they humbly conceived I had not proved my point, and that Milton might have written as he has done, supposing he had never seen these authors, or they had never existed. Such is the force of prejudice! This exactly confirms the judicious observation of the excellent moralist and poet :

Pravo favore labi mortales solent,
Et pro judicio dum stant erroris sui,
Ad pænitendum rebus manifestis agi.

For had I designed (as the vindicator of Milton supposes) to impose a trick on the public, and procure credit to my assertions by an imposture, I would never have drawn lines from Hog's translation of Milton, a book common at every sale, I had almost said at every stall, nor ascribed them to authors so easily attained : I would have gone another way to work, by translating forty or fifty lines, and assigning them to an author, whose works possibly might not be found till the world expire at the general conflagration. My imposing therefore on the public in general, instead of a few obstinate persons (for whose sake alone the stratagem was designed) is the only thing culpable in my conduct, for which again I most humbly ask pardon: and that this, and this only was, as no other could be, my design, no one I think can doubt, from the account I have just now given; and whether that was so criminal, as it has been represented, I shall leave every impartial mind to determine.

AN ACCOUNT

OF AN

ATTEMPT TO ASCERTAIN

THE

LONGITUDE. *

FIRST PRINTED IN THE YEAR MDCCLV.

It is well known to seamen and philosophers, that after the numerous improvements produced by the extensive commerce of the later ages, the great defect in the art of sailing is ignorance of longitude, or of the distance to which the ship has passed eastward or westward, from any given meridian.

That navigation might be at length set free from this uncertainty, the legislative power of this kingdom incited the industry of searchers into nature, by a large reward proposed to him who should show a practicable method of finding the longitude at sea ; and proportionable recompences to those, who, though they should not fully attain this great end, might yet make such advances and discoveries as should facilitate the work to those that might succeed them.

* An Account of an attempt to ascertain the Longitude at Sea, by an exact Theory of the Variation of the Magnetical Needle ; with a Table of Variations at the most remarkable cities in Europe, from the year 1660 to 1860. By Zachariah Williams.

By the splendor of this golden encouragement many eyes were dazzled, which nature never intended to pry into her secrets. By the hope of sudden riches many understandings were set on work very little proportioned to their strength, among whom whether mine shall be numbered, must be left to the candour of posterity: for I, among others, laid aside the business of my profession, to apply myself to the study of the longitude, not indeed in expectation of the reward due to a complete discovery; yet not without hopes, that I might be considered as an assistant to some greater genius, and receive from the justice of my country the wages offered to an honest and not unsuccessful labourer in science.

Considering the various means by which this important enquiry has been pursued, I found that the observation of the eclipses, either of the primary or secondary planets, being possible but at certain times, could be of no use to the sailor ; that the motions of the moon had been long attended, however accurately, without any consequence; that other astronomical observations were difficult and uncertain with every advantage of situation, instruments and knowledge ; and were therefore utterly impracticable to the sailor, tost upon the water, ill provided with instruments, and not very skilful in their application.

The hope of an accurate clock or time-keeper is more specious. But when I began these studies, no movements had yet been made that were not evidently unaccurate and uncertain : and even of the mechanical labours which I now hear so loudly celebrated, when I consider the obstruction of movements VOL. X.

2 B

by friction, the waste of their parts by attrition, the various pressure of the atmosphere, the effects of different effluvia upon metals, the power of heat and cold upon all matter, the changes of gravitation and the hazard of concussion, I cannot but fear that they will supply the world with another instance of fruitless ingenuity, though I hope they will not leave upon this country the reproach of unrewarded diligence.

I saw therefore nothing on which I could fix with probability of success, but the magnetical needle, an instrument easily portable, and little subject to accidental injuries, with which the sailor has had a long acquaintance, which he will willingly study, and can easily consult.

The magnetic needle from the year 1300, when it is generally supposed to have been first applied by John Goia, of Amalphi, to the seaman's use, seems to have been long thought to point exactly to the north and south by the navigators of those times; who sailing commonly on the calm Mediterranean, or making only short voyages, had no need of very accurate observations; and who, if they ever transiently observed any deviations from the meridian, either ascribed them to some extrinsic and accidental cause, or willingly neglected what it was not necessary to understand.

But when the discovery of the new world turned the attention of mankind upon the naval sciences, and long courses required greater niceties of practice, the variation of the needle soon became observable, and was recorded in 1500 by Sebastian Cabot, a Por

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