Yale Digital Edition of the Works of Samuel Johnson

Table of Contents

An Account of an Attempt to Ascertain the Longitude by Sea, by an Exact Theory of the Variation of the Magnetical Needle

- Export Citation
- Export Annotation

By Johnson, Samuel

Samuel Johnson: Johnson on Demand

Image view

Print
Save
Share
Cite

Translation

AN ACCOUNT OF AN ATTEMPT TO ASCERTAIN THE LONGITUDE BY SEA, BY AN EXACT THEORY OF THE VARIATION OF THE MAGNETICAL NEEDLE (1755)

[Editorial Introduction]

Johnson wrote this work for Zachariah Williams, the father of his friend and frequent housemate Anna Williams, with an Italian translation on facing pages composed by Giuseppe Baretti. It was printed for Johnson’s principal publisher Robert Dodsley and John Jeffries and sold by Joseph Bouquet, the publisher (with John Payne) of the Rambler. Johnson presented a copy to the Bodleian Library, writing on a flyleaf opposite the half-title page, “Zachariah Williams, died July 12. 1755 in his eighty third year.” He, or someone else, also pasted into this copy, on the half-title page, a copy of Johnson’s obituary of Zachariah Williams from an unidentified newspaper. The obituary appears in volume XIX of the Yale Edition (p. 486). On the English title page, which is a verso, facing the Italian title page, Johnson wrote underneath the author’s name, “aged LXXXII.” At the bottom of “A Correct Table of the Magnetical Variations, at the most remarkable Cities in Europe. Commencing A.D. 1660, & Ending 1860” Johnson wrote, “The author of this table died July 12. 1755 in the eighty third year of his age.” He also wrote “aged 82,” after the statement at the bottom of the table, “This table formed upon the true Doctrine of Magnetism in the year 1754. is recommended to the notice of posterity by Zachariah Williams.” The Bodleian copy provides our copy-text. The Oxford Dictionary of National Biography was particularly useful to us in assembling the notes on this text.

An Account, &c.

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,

Page 229

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.1

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,2 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,3 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,

Page 230

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.4 But when I begun 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 by friction, the waste of their parts by attrition, the various pressure of the atmosphere, the effects of different effluvia5 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,6 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.

Page 231

But when the discovery of the new world turned the attention of mankind upon the naval sciences, and long courses7 required greater niceties of practice, the variation of the needle soon became observable, and was recorded in 1500 by Sebastian Cabot, a Portuguese, who, at the expence of the king of England, discovered the northern coasts of America.8

As the next century was a time of naval adventures, it might be expected that the variation once observed, should have been well studied: yet it seems to have been little heeded; for it was supposed to be constant, and always the same in the same place, till in 1625 Gellibrand noted its changes, and published his observations.9

From this time the philosophical world1 had a new subject of speculation, and the students of magnetism employed their researches upon the gradual changes of the needle’s direction, or the variations of the variation, which have hitherto appeared so desultory and capricious, as to elude all the schemes which the most fanciful of the philosophical dreamers could devise for its explication. Any system that could have united these tormenting diversities they seem inclined to have received, and would have contentedly numbered the revolutions of a central magnet, with very little concern about its existence, could they have assigned it any motion or vicissitude of motions which would have corresponded with the changes of the needle.

Yet upon this secret property of magnetism I ventured to build my hopes of ascertaining the longitude at sea. I found it undeniably certain that the needle varies its direction in a course eastward or westward between any assignable parallels of latitude: and supposing nature to be in this as in all other operations uniform and consistent, I doubted not but

Page 232

the variation proceeded in some established method, though perhaps too abstruse and complicated for human comprehension.

This difficulty however was to be encountered; and by close and steady perseverance of attention I at last subdued, or thought myself to have subdued it; having formed a regular system in which all the phaenomena seemed to be reconciled; and being able from the variation in places where it is known to trace it to those where it is unknown; or from the past to predict the future: and consequently knowing the latitude and variation, to assign the true longitude of any place.

With this system I came to London, where having laid my proposals before a number of ingenious gentlemen, it was agreed that during the time required to the completion of my experiments, I should be supported by a joint subscription to be repaid out of the reward, to which they concluded me entitled. Among the subscribers was Mr. Rowley, the memorable constructor of the orrery;2 among my favourers was the Lord Piesley, a title not unknown among magentical philosophers.3 I frequently shewed upon a globe of brass, experiments by which my system was confirmed, at the house of Mr. Rowley, where the learned and curious of that time generally assembled.4

At this time great expectations were raised by Mr. Whiston, of ascertaining the longitude by the inclination of the needle, which he supposed to increase or diminish regularly.5 With this learned man I had many conferences, in which I endeavoured to evince what he has at last confessed in the narrative of his life, the uncertainty and inefficacy of his method.6

About the year 1729, my subscribers explained my pretensions

Page 233

to the lords of the admiralty, and the Lord Terrington7 declared my claim just to the reward assigned in the last clause of the act to those who should make discoveries conducive to the perfection of the art of sailing. This he pressed with so much warmth, that the commissioners agreed to lay my tables before Sir Isaac Newton, who excused himself, by reason of his age, from a regular examination: but when he was informed that I held the variation at London to be still increasing; which he and the other philosophers, his pupils, thought to be then stationary, and on the point of regression, he declared that he believed my system visionary.8 I did not much murmur9 to be for a time overborn by that mighty name, even when I believed that the name only was against me: and I have lived till I am able to produce, in my favour, the testimony of time, the inflexible enemy of false hypotheses;1 the only testimony which it becomes human understanding to oppose to the authority of Newton.

My notions have indeed been since treated with equal superciliousness by those who have not the same title to confidence of decision; men who, though perhaps very learned in their own studies, have had little acquaintance with mine. Yet even this may be born far better than the petulance of boys whom I have seen shoot up into philosophers by experiments which I have long since made and neglected, and by improvements which I have so long transferred into my ordinary practice, that I cannot remember when I was without them.

When Sir Isaac Newton had declined the office assigned him, it was given to Mr. Molineux, one of the commissioners of the admiralty, who engaged in it with no great inclination to favour me;2 but however thought one of the instruments,

Page 234

which, to confirm my own opinion, and to confute Mr. Whiston’s, I had exhibited to the admiralty, so curious or useful, that he surreptitiously copied it on paper, and clandestinely endeavoured to have it imitated by a workman for his own use.

This treatment naturally produced remonstrances3 and altercations, which indeed did not continue long, for Mr. Molineux died soon afterwards; and my proposals were for a time forgotten.

I will not however accuse him of designing to condemn me, without a trial; for he demanded a portion of my tables to be tried in a voyage to America, which I then thought I had reason to refuse him, not yet knowing how difficult it was to obtain, on any terms, an actual examination.

About this time the theory of Dr. Halley was the chief subject of mathematical conversation;4 and though I could not but consider him as too much a rival to be appealed to as a judge, yet his reputation determined me to solicit his acquaintance and hazard his opinion. I was introduced to him by Mr. Lowthrop and Dr. Desaguliers,5 and put my tables into his hands; which, after having had them about twenty days under consideration, he returned in the presence of the learned Mr. Machin,6 and many other skilful men, with an entreaty “that I would publish them speedily; for I should do infinite service to mankind.”

It is one of the melancholy pleasures of an old man to recollect the kindness of friends, whose kindness he shall experience no more. I have now none left to favour my studies; and therefore naturally turn my thoughts on those by whom I was favoured in better days: and I hope the vanity of age may be

Page 235

forgiven, when I declare that I can boast among my friends, almost every name of my time that is now remembered: and that in that great period of mathematical competition scarce any man failed to appear as my defender, who did not appear as my antagonist.

By these friends I was encouraged to exhibit to the Royal Society, an ocular proof of the reasonableness of my theory by a sphere of iron, on which a small compass moved in various directions, exhibited no imperfect system of magnetical attraction. The experiment was shown by Mr. Hawkesbee,7 and the explanation, with which it was accompanied, was read by Dr. Mortimer.8 I received the thanks of the society: and was solicited to reposit my theory properly sealed and attested among their archives, for the information of posterity. I am informed, that this whole transaction is recorded in their minutes.

After this I withdrew from public notice, and applied myself wholly to the continuation of my experiments, the confirmation of my system, and the completion of my tables, with no other companion than Mr. Gray, who shared all my studies and amusements, and used to repay my communications of magnetism, with his discoveries in electricity.9 Thus I proceeded with incessant diligence; and perhaps in the zeal of enquiry did not sufficiently reflect on the silent encroachments of time, or remember, that no man is in more danger of doing little, than he who flatters himself with abilities to do

Page 236

all.1 When I was forced out of my retirement,2 I came loaded with the infirmities of age, to struggle with the difficulties of a narrow fortune, cut off by the blindness of my daughter,3 from the only assistance which I ever had, deprived by time of my patrons and friends, a kind of stranger in a new world, where curiosity is now diverted to other objects, and where, having no means of ingratiating my labours, I stand the single votary of an obsolete science, the scoff of puny pupils of puny philosophers.4

In this state of dereliction and depression, I have bequeathed to posterity the following table:5 which, if time shall verify my conjectures, will shew that the variation6 was once known; and that mankind had once within their reach an easy method of discovering the longitude.

I will not however engage to maintain, that all my numbers are theoretically and minutely exact: I have not endeavoured at such degrees of accuracy as only distract enquiry without benefitting practice. The quantity of the variation has been settled partly by instruments, and partly by computation: instruments must always partake of the imperfection of the eyes and hands of those that make, and of those that use them: and computation, till it has been rectified by experiment, is always in danger of some omission in the premises, or some error in the deduction.

Page 237

It must be observed, in the use of this table, that though I name particular cities for the sake of exciting attention, yet the tables are adjusted only to longitude and latitude. Thus when I predict that at Prague, the variation will in the year 1800 be 24¼ W. I intend to say that it will be such if Prague be as I have placed it after the best geographers in longitude, 14 30′. E. latitude 50 40′. but that this is its true situation I cannot be certain.7 The latitude of many places is unknown, and the longitude is known of very few; and even those who are unacquainted with science will be convinced that it is not easily to be found, when they are told how many degrees Dr. Halley, and the French mathematicians, place the Cape of Good Hope distant from each other.8

Those who would pursue this enquiry with philosophical nicety, must likewise procure better needles than those commonly in use. The needle, which after long experience I recommend to mariners, must be of pure steel, the spines and the cap of one piece, the whole length three inches, each spine containing four grains and a half of steel, and the cap thirteen grains and a half.

The common needles are so ill formed, or so unskilfully suspended, that they are affected by many causes besides magnetism: and among other inconveniencies have given occasion to the idle dream of a horary variation.9

I doubt not but particular places may produce exceptions to my system. There may be, in many parts of the earth, bodies which obstruct or intercept the general influence of magnetism;

Page 238

but those interruptions do not infringe the theory. It is allowed, that water will run down a declivity, though sometimes a strong wind may force it upwards. It is granted, that the sun gives light at noon, though in certain conjunctions it may suffer an eclipse.

Those causes, whatever they are, that interrupt the course of the magnetical powers, are least likely to be found in the great ocean, when the earth, with all its minerals, is secluded from the compass by the vast body of uniform water. So that this method of finding the longitude, with a happy contrariety to all others, is most easy and practicable at sea.

This method, therefore, I recommend to the study and prosecution of the sailor and philosopher; and the appendant specimen I exhibit to the candid1 examination of the maritime nations, as a specimen of a general table, shewing the variation at all times and places for the whole revolution of the magnetic poles, which I have long ago begun, and, with just encouragement, should have long ago compleated.

Page 239

Editorial Notes

1 The Longitude Act was passed by Parliament in July 1714 at the end of Queen Anne’s reign. It established prizes for work on ascertaining longitude at sea. For a history of the problem and its solution, see Dava Sobel, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time (1995).

2 Williams’s “profession” seems to have been scientist or “projector”; he was known for his skill in magnetics.

3 Primary planets orbit the sun, whereas secondary planets orbit another planet. Astronomers such as Galileo, Ole Rømer (1644–1710), and John Flamsteed (1646–1719) believed longitude could be determined by observations of eclipses (for a summary, see Sobel, Longitude, pp. 21–33).

4 Specious: likely. This was the method successfully pursued by the clock-maker John Harrison (1693–1776); he solved the problem by 1765 but was not fully recognized for his work until 1776.

5 Effluvia: “A stream of minute particles, formerly supposed to be emitted by a magnet, electrified body, or other attracting or repelling agent, and to be the means by which it produces its effects” (OED).

6 William Gilbert, De Magnete (1600), is the ultimate source of SJ’s history, though he may have read any number of writers who cited Gilbert. Gilbert mentions Goia (citing Flavius Blondus) and dates his use of the magnet in navigation to 1301 (p. 4).

7 Course: “Onward movement in a particular path” (OED, 2a).

8 Gilbert says Sebastian Cabot (1481/2–1557) first noticed variations in the magnetic needle (p. 4). ODNB says he was born in Venice to a Genoese father and a Venetian mother.

9 Henry Gellibrand (1597–1637), A Discourse Mathematical on the Variation of the Magneticall Needle (1635). “1625” seems to be a mistake.

1 “Philosophical world”: scientific community.

2 John Rowley of Lichfield (1668?–1728), whom SJ mentions admiringly in Adventurer 99 (16 October 1753), Yale, II.433. Cf. Reade, III.135–36.

3 James Hamilton, Lord Paisley (1686–1744), author of Calculations and Tables Relating to the Attractive Power of Loadstones (1729).

4 Rowley lived in Johnson’s Court, off Fleet Street, where SJ himself later lived and quite near his then residence in Gough Square.

5 William Whiston (1667–1752), author of The Longitude and Latitude Found by the Inclinatory or Dipping Needle (1721) and other works on longitude.

6 Whiston, Memoirs (1749–50; 2nd ed., 1753).

7 George Byng, Lord Torrington (1663–1733), naval commander and father of Admiral John Byng, whose trial and execution in 1756–57 SJ deplored (see Yale, X.213–60).

8 Visionary: “purely ideal or speculative; fantastic, impractical” (OED, 3b).

9 Murmur: complain.

1 For SJ on the “test of time,” see, e.g., Rambler 92 (Yale, IV.121–130).

2 Samuel Molyneux (1689–1728), MP and astronomer.

3 Remonstrances: protestations.

4 Edmond Halley (1656–1742), the second astronomer royal (following John Flamsteed), famous for predicting the positions of heavenly bodies (including Halley’s Comet) for centuries to come.

5 John Lowthrop (1659–1724) was a Fellow of the Royal Society and editor of its abridged Transactions. He worked on engineering projects for the Duke of Chandos with John Theophilus Desaguliers (1683–1744), scientist and engineer, defender of Newtonian theories, and popular lecturer.

6 John Machin (1686?–1751), astronomer and secretary of the Royal Society from 1718–47.

7 Francis Hauksbee (1688–1763), instrument-maker and nephew of Francis Hauksbee the elder (d. 1713), collaborated with William Whiston on his longitude project.

8 Cromwell Mortimer (c. 1693–1752), acting secretary to the Royal Society (1730–52).

9 Stephen Gray (1666–1736), experimenter and assistant to Desaguliers, was Williams’s fellow pensioner at the Charterhouse and a close friend. For information on Gray’s theories, see David H. Clark and Stephen P. H. Clark, Newton’s Tyranny: The Suppressed Scientific Discoveries of Stephen Gray and John Flamsteed (2001). In her Miscellanies (1766), Anna Williams published her poem “On the Death of Stephen Grey [sic], F. R. S., the Author of the Present Doctrine of Electricity.” A note in the Miscellanies asserts that Anna “was the first that observed and noticed the emission of the electrical spark from a human body” (p. 42). For more on the Miscellanies, including SJ’s involvement in the project, see pp. 200 above and 486 below.

1 The danger of hesitating to choose one course or another is one of SJ’s favorite themes; see, e.g., Rambler 135, penultimate paragraph (Yale, IV.349), and Rasselas (Yale, XVI.111): “while you are making the choice of life, you neglect to live.”

2 Williams was forced to leave the Charter-House, Sutton’s Royal Hospital, partly because his daughter was living there. He appealed his expulsion in A True Narrative of certain Circumstances Relating to Zachariah Williams (1749), which included several letters of appeal by his daughter Anna in two separately paginated appendices.

3 According to Nichols, she lost her sight in 1740 (Lit. Anec., 2.179n).

4 Cf. SJ’s description of himself after the death of his wife: “a solitary wanderer in the wild of life. . . . A gloomy gazer on a World to which I have little relation” (Letters, I.90).

5 “A Correct Table of the Magnetical Variations, at the most remarkable Cities in Europe. Commencing A.D. 1660, & Ending 1860.”

6 Variation: “the deviation or divergence of the magnetic needle from the true north and south line” (OED, 5a).

7 The coordinates are now given as 50.08 N, 14.42 E.

8 The French mathematicians may be Giovanni Domenico Cassini (1625–1712) and Le Sieur de St. Pierre. Halley’s New and Correct Sea Chart of the Whole World, shewing the Variations of the Compass as they were found in the year M.D.CC was first published in 1702. Halley’s figures for the Cape of Good Hope were vindicated by M. de May, “a missionary, who went with M. de Tournon, the pope’s legate to China” (“Reflections on the Observations of the Variation of the Needle, Made in the Pope’s Legate’s Voyage to China, in the Year 1703, by M. Cassini the Son; Translated by Mr. Chambers” in The Philosophical History and Memoirs of the Royal Academy of Sciences at Paris, trans. and abridged, John Martyn and Ephraim Chambers [1742], pp. 239–45).

9 Horary variation: a table or figure predicting the variation at any place.

1 Candid: unbiased.

Transcription

Document Details

Document TitleAn Account of an Attempt to Ascertain the Longitude by Sea, by an Exact Theory of the Variation of the Magnetical Needle

AuthorJohnson, Samuel

Creation Date1755

Publ. DateN/A

Alt. TitleN/A

Contrib. AuthorN/A

ClassificationSubject: Zachariah Williams; Subject: Navigation; Subject: Longitude Act; Subject: Science; Subject: Magnetism; Subject: Isaac Newton; Subject: Edmond Halley (+ other scientists); Subject: The Royal Society; Subject: Anna Williams; Subject: Magnetic needle; Genre: Scientific; Genre: Essay; Genre: Treatise

PrinterN/A

PublisherRobert Dodsley and John Jeffries

Publ. PlaceLondon

VolumeSamuel Johnson: Johnson on Demand

Login Required

Your subscription has expired.