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Mr. URBAN,
Summerland place,

could at all sanction the supposition Exeter, Dec. 15. of their actuality. This certainly N

Poles are more real sive circulation, you have, occasion and that all future Theories of Va. ally, done me the favour to insert riation must, gecessarily, be deduced some dissertations of mine, on scien. from the well-known attraction of tific subjects.

the North and South Poles of the No event will be deemed more Earth, combined with the ascertained remarkable by future ages, than the action of the North-west Magne decided discovery of the actual ex Pole, whose positive discovery reistence of a North-west Magnetic flecis so much credit on the present Pole, by the hardy and enterprizing age.--This is still further confirmed Navigators of the passing century. by a general remark to be made on The vast importance of the fact is the variations of Cook ; viz. that in of the utmost consequence, as it Southern Latitude particularly, they must, infallibly, in time, lead to cer. were, in East and West Longitude, taio Theory of the difference of the of opposite descriptions, and decidedly variations of the Magnetic Needle. iofluenced, relatively, by the MagDr. Halley had recourse to the sup

netic Pole, whose position is now position of four Magnetic Poles be. nearly known. Had the Southern longing to Magnetic nucleus Poles existed, the approximation to revolving within the Earth, from their imagined situations, by several East to West; and thus he attempts Circumoavigators, must, from the ed to account for the variation, and known laws of Magnetism, have its changes, supposed to have been giveo rise lo so strong an attraction first observed by Columbus and Se- of the South end of the Magnetic bastian Cabot.-Euler, under a very Needle, as would have made the vaplausible and ingenious Theory, riation three times, at least, greater supposed only two Magnetic Poles. than it has proved ; independent of Mr. Churchman adopted the idea of causing it to be of a different nature two Magaetic Poles ; and imagined from what actually appears in the the Northern one to move Eastward, records of Voyages, -Thus then, this on a parallel of Latitude, while the interesting subject seems to be rea. Southern moved slower; the former sonably cleared from the embarrasstaking 1096 years in its revolution, ment of Southero Magnetic Poles, while the latter required 2289. The beyond the requisite one of the South North-west Pole was supposed by end of the Earth's axis : and all futhese Philosophers to be situated pót tore reasoning (lill experience and far from where the recent discovery experiment carry us farther) must has placed it. The deflection of the be founded less on hypothesis, and Needle has been found by the Navi. more on fact, than has hitherto boen gators in the Discovery.ships, to have the case. exceeded one-fourth of a great cir Having premised thus much, cle. Captain Cook in bis voyages, come to the consideration of the approached nearly in the South he wonderful and inexplicable phenomisphere, to the supposed situations menon in nature, the accoupling for of ihe South Magnetic Poles, and which has induced 10 mapy eminent found do quantum of variation that scientific characters to form the

Thcorics

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Theories briefly mentioned above. Theors might be arrived at but Professor Gillebrand having com when the contrary proves to be the pared his own observations of the fact, the attempts made to lay down variation with those of others, as on the Globe a curve of no magnecertained that it gradually increased tic, variation, is useless, if not absurd. Westward. In the year 1576 the A small Needle compared to a large variation was found to be 11° 15' real Magnet, is experimentally found East, in London. It diminished gra

to furnish a similar effect to a Magdually till 1662 (or 1657, by other netic Compass-card, acted on by accounts), when it became nothing; some in visible magnetic power within or in other words, the Magnetic the body of the Earth. This leads Needle pointed to the true Norih. In to the certain conclusion, that the 1666, Mr. Sellers made the variation changes in variation, and those much 0° 34' West. Since that period the less in dip, arise from a correspondvariation has been increasing West- ing change or movement in the ward, and during the three last years

I have made the remarks it has remained nearly stationary contained in this paper because I am Io comparing its progress during si- led to believe that the recent discomilar periods, it does not appear that very of a North-west Magnetic Pole the rate of increase is equable, as it has put it in the power of experivaries from one or two minutes, to mental philosophy to establish, in a medium annual increase of 9'48". time, the law of Movement of the In the Royal Society's Rooms, the Magnetic cause producing effects mean variation in June 1817 which have hitherto baffled all hu24° 17' 54"; and in June 1818 it was

research. The anomalies of in mean quantity 24° 17'. In June the variation observed by different 1819, it was found to be 24° 15' 43" ; persons in the same year, in London, from which it would seem that it had clearly evince that the application of begun to returo. It was found, by a needle to a Meridian-line accu. Captain Cook, that the sume obe rately laid down, can alone furnish servers, with the same compass, in the precise variation at tbe place of the same day, made a difference of observation.-In two papers by me, 5 and 6 degrees; and nearly the in the Philosophical Transactions for double of this was found as a dif. 1796 and 1798, the process of laying ference between the variation taken off such a Meridian is described; and on the ice, and on board-ship in Baf

this was done for the purpose of asfin's Bay. This leads to the clear certaining accuratels, not only the conclusion, that observations on terru variation, but also the variation of firma, can alone be depended upon the variation, or the diornal vibral. for real accuracy.

ing variation, at Bercoolen or SuThe dip of the Needle, or its in matra ; and afterwards, at the Island clination io the nearest Pole (and I of St. Helena. Professor Gillebrand have some reason to conclude that first noticed this diurnal variation, this also is subject to a daily small in 1635. This vibratiog variation variation), was an accidental disco. moves and returns through a few very, made by Mr. Norman, in ba minutes of a degree, daily; and in lancing bis Needles. It was in 1576 different places its direction and found to be 71° 50' at London ; and quantity do not correspond. Many in June 1819 it was about 70° 51' Theories have been formed, in order in the Royal Society's Rooms. In to account for this extraordinary the very same situation, at different Magnetic phenomenon; and the experiods, both the variation and dip periments made by the application of are different ; and the dip does not heat to Magnets, afford, probably, correspond to change in Latitude the most plausible solution of the under the same meridian ; nor is the case : but a series of accurate obsersame dip given by the same dippiog vations on Meridians, in many disneedle, at sea, on the same day. This tant situations, are requisite to reagain indicates the necessity of ob move serious objections lying agaiost serving tlie dip also on shore, when the best-imagined of these conjectureal accuracy is wanted. If the va ral Theories. riation and dip were not constantly From the dip of the Needle it is altering in the same place, a certaio quile unquestionable that the Mag

1820.] Col. Macdonald on the North-West Magnetic Polé. 485 netic power, or cause, lies at some variation at Bencoolen was 1° mag' to uoknown depth under the surface of 1° 11' East ; the vibrating variation the Earth. Mr. Æpinus, of the In- giving a returning swing of about perial Academy of St. Petersburgh, four ininutes of a degree. Captain has distinctly traced the close and in Cook found the variation in the timate analogy between Magnetism Straits of Sunda, to be 1° West.-At and Electricity : and the Galvanic Condore in 8° 6' North, and 106° 18' experiments lately made by the East Longitude, the variation was 0° Prince of Chemisis, Sir Humphrey 14 West. Now these, and many Davy, place the fact beyond all other places of nearly do variation, doubt. Experiments shew that a sub are nearly in the line, vertical plane, tle fluid of these united descriptions or section of the two Poles ; and, pervades the atmosphere, and iron, consequently, the variation must, magnetised and otherwise ; forming necessarily, be little or nothing. a constant and invisible communica: The well-known fact that the varia: tion between the Magretic cause tiou is constantly changing in one within the Earth and cominon Mag- and the same place, furnishes no netic Needles. There is now every small proof in favour of the Theory reason to conclude, that the Aurora of Movement of the Secondary Mag. Borealis constitutes a Magnetic cur. netic Cause, or North-west Magnetic rent between the real North Pole Pole.--The variation in London, was and the North-west Magnetic Pole ; nothing in 1662, or 158 years ago. the one giving out to the other an Supposing the New Pole to be situexcess of fluid, in order to restore ated in 1000 of West Longitude, it an equilibrium between positive and would require 568 years, 9 months, negative quantities. This supposi. and 18 days, to effect its revolution tion may not be quite gratuitous, as under the parallel of its supposed we generally observe the Aurora Bo movement. - 11 243 years the dip realis to aci io tbis directivo.

of the Needle appears to have diIl is utterly impossible to attempt mioished in London only 59 minutes to account for the constant increase of a degree. This would seem to inof the variation, without supposing dicate that the movement of the that the North west Magnetic Pole Magnet Pole is more in a straight has a constant molion rouod the line, nearly in an East and West diNorth Pole of the Earth in Longi- rection, than in a circular or elliptude, on a parallel of Latitude; or tical curve, round the North Pole of in an Elliptic Curve. Though the the Earth. Bond makes the variavariation, when first discovered, was tion nothing in London jo 1657. only 11° 15' East, there can be lilile The observations regularly taken by doubt but that those who are des. our Librarian, at the rooms of the tined to exist in the year 2040, or Royal Society, may be relied on. It about that period, will tind the va would appear from them, that the riation as much East, as it is now West variation has ceased, or turned. West. The North Pole appears to The variation, therefore, has taken attract more powerfully than the allowing the change to have been North-west Magnetic Pole, as must in 1818) about 161 years to attain its be the case on the supposition of a utmost Westing. It being reasonrevolutionary movement indispens- able to suppose that the Magnetic able for the formation of any toler Pole will move as far to the East as able Theory of the Variation. The it has to the West of the Meridian great difficulty in the way of a of London, the whole period of its Theory of Magnetic Revolution, movement in a straighi line within arises from that of accounting for the Earth, from West to East, will the fact of no variation found in be thus 322 years. – Io the year some places. The solution of this 1600 the variation at St. Helena was difficulty may be found in a fair sup go East. In 1692 it was 1° West. position, that the North Pole, the lo 1796 I make it there, from a me. Moving Magnetic Pole, and the place dium of morning and evening obser. of ou variation on the surface of the vations on a Meridian, 15° 48' 34".5; Earth, may be at the time nearly in while in London, in 1795, it was 23o

I found, by continued obo 57.-It is experimentally found, that servations during two years, that the Magnetic action, like that of heat,

diminishes,

one line.

dimipishes inversely, as the squares sheltered by a small building deroid of the distaoces. Again, the South

of iron. Careful observations made, Pole, after passing the Equator, at- anoually, for a few years, on this tracts the South end of the dipping Meridian, would clearly determine Needle (which must, necessarily, pos whether or not the Nortb-west Magsess a Norih polarity), and the East netic Pole had a movement, and the and West variation in South Latitude direction and annual quantity of such are generally less than in siinilar si. movemeot, if thus found to take tuations in the Northern hemispbere. place. Huts, but no natives, have The action of the South Pole, com been seen in these hyperborean rebined with the other cause stated, gions. If, however, batives should may go far in accounting for this appear next year, the Meridian, to anomaly.

remain uudisturbed, might be conIt was essentially necessary to take cealed in ao excayation, or situated the foregoing view of this most won. in some secret place. derful and interesting subject, pre

The observation of the variation viously to recommending the com- of the variation, on this Meridian), mencement of a most iinportant 8c would be an important object of unries of experiments calculated to as remitting attention. lo my papers certain decidedly, whether the re. I ascribed it to the action of the cently discovered North-west Mag. Sun's beat, increased and diminished Detic Pole has, or has not, a peri. during the Earth's revolution on its odical movement corresponding to axis. I venture to conjecture, that East and West variation, increasing this species of variation will (on the and decreasing, as has been observed. principle of heat acting on the --There can be but one infallible Northern Poles, alternately) be found mode of inaking this grand and con lo move in an opposite direction to clusive experiment, and I take your

that observed in London. Should widely-circulating and valuable Pub- this prove to be the fact, the cause Jication as the channel through which

of the diurnal variation will be thus I earnestly call the allentiou of Phi- completely set at rest. The utmost losophers and Men of Sciencé, to a efforts will be made to ascertain tbe sublime discovery, which British dar. precise position of the new Pole ; ing and fearless enterprise has, at and if it should be impracticable to length, put within the reach of pa

make the essential observations sug. tient and accurate investigation.

gested, io its vicinity, the purpose The position of the North-West will be equally answered by taking Magnetic Pole has been approxi- them to The East of Copper Mine maled, to a moral certainty.-i take River, at the point where West va. it for granted, that the discovery. riation ceases, and East commences. ships will proceed again to explore The Regeot's Channel may, proba. to the utmost the channels in the bly, lead to this situation ; if not, it Polar Basin, to the Westward of can be atlained to over-land, from Baffiu's Bay. The principal object the North-west of Hudson's Bay. must be the ascertaining precisely If the discovery I suggest in these the position of ibe vew Pole, or î imperfect statements is made in due would rather denominate it, the mov. time, it will be the greatest and most ing mugnetic power, of whose exist importaal in Scientific History: and euce no farlher doubt can remain.. it is by giving circulation and pub. This having been happily achieved licity to Papers of this description, by the bold Commander, and by his that such valuable results can be ar. companions, who have deserved so

rived at. John MACDONALD. much of their Country, a Meridian should be accurately laid off, at sonie

Mr. URBAN,

Nov. 27.

scription of Monument to cumference and Needle applied to General Sir Thomas Pictop, io St. this Meridian, vught in principle and Paul's, appeared is your Magazine construction, to resemble those used

* In alluding lo Col. Macdonald's article, by me, and described in the Papers (p. 546, note) the word.Co!' was inadvertI have alluded to. The Meridian ently omitted during a part of the impres. sustained by a strong post, inight be sion.

(p. 368),

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1820.) A. Copinger.-Joe Miller.- Improved Direction Posts, 487 (p. 368), I beg to subinit the fol. Time had nearly obliteraled, has been lowing as the idea which I meant preserved and transferred to this stone, thal group to convey :

by order of Mr. JARVIS Buck, Church. “ Genius and Valour rewarded by Vic

warden, A.D. 1816.” tory. - This group is surmounted by a Yours, &c.

J. W. Bust of the Hero. On the Pillar is intro. duced the losignia of the Orders of the Baththe Grand Cross--and the Portu

Wickham Skeith,

Mr. URBAN, guese Order of the Castle and Sword.

Suffolk, Dec. 12. Yours, &c. S. GAHAGAN. N this improving age, when all

The active part of mankind are Mr. URBAN, Oxford, Dec. 9. alert to juvent for the benefit of the N answer to “ CARADOC,” (p. 290), Publick ; I send a few particulars re

Ambrose Copinger, esq. (not Coi specting my invented direction Post tioger) was Lord of the Manor of Hil. (for cross roads) noticed in p. 290. liogdon in Middlesex, and patron of The first thought of my in veotion that Church, to which he presented a

was as follows. I live in the wood. reclor iu 1599, and another in 1603. lands of Suffolk, about eight miles His Ambrose Copinger, esq. was

from Slow-market. My father coinknighted in 1602 ; and died in 1605. ing home on a dark night from that The date of his Academical Degrees, town, lost his way, and was found it is hoped, some Cambridge Corre- dead dext moruing, within a mile of spondeni may supply.

his own collage. Ever since it has Queen Elizabeth's visit to Sir Wil. been impressed upon my mind that liam Russel at Chiswick, in August Direction Posts might be so contrived 1602, is noticed by Mr. Lysons, from as to be seen in the dark, and, after the printed “ Progresses ;” with the mary experiments, I can prove that additional information, that a copy

all painted letlers may be so of the “Speeches'

was sent to Sir trived as to be seen io the night as Robert Sydney. Can these now be well as the day, for as light is a real found in the Papers of that Family? substance, I have contrived to make Or (which is more probable) has a

letters that will retain that substance, copy of them been discovered, by the and emit it when the sun is under the researches of the ingenious Lord John earth. This quality will continue seRussell, among the many valuable veral years, and at the end of that Documents of that antient and illus- time may be renewed with the greattrious Family in the archives of Wo est dispatch. As this is a great merburn Abbey? It was certainly cus. cauțile kingdom, if every parish was tomary to present copies in Ms. of compelled to have Direction Posts of similar Speeches, Devices, and En lbis description, it would be a great tertainmeuts, among those who bad National improvement, and would the hooour and the expence of enter

save the lives of many. Let any man taining the Virgin Queen.

paiot in his imagination all the Cross Yours, &c. ANTIQUARIUS.

Roads furnished with these Direction

Posts; and he must confess it an inMr. URBAN,

Dec. 11. provement highly requisite, indepenOUR

dently of the many purposes it may be (p. 327), has fallen into an error

turned to at present unthought of. in his account of the famous Jester, If backoey coaches were numbered Joe Miller. The place of juterment with this, they might easily be disof the renowned Comedian was put tinguished in the night in dark streets ; the “ East side of St. Clernent Danes" as also watchmen's coats might be (Cburch I suppose). He lies buried numbered thus, which would be a in the Upper Cburch-yard of that guard for their conduct, and exParish, situate in Portugal.street, tremely useful to the Police Depart. near Lincoln's Ion, where his Torubé ment, &c. &c. stope now stands, with the loscrip Being placed in that part of the tion (as already given in p. 321] country which is destitute of men of will the following modern addition : science, I beg of you to insert this in

“ From respect to social worth, mirth. your useful Magazine, in hopes that ful qualities, and histrionic excellence,

some benevolent Gentleman will encommemorated by poetic talent in hun. able ine to bring it forward for the blo, life, the above lascription, which benefit of the publick.' I can shew

the

,

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