He who erst the city freed

From the winged virgin's power, Charge him not with such a deed, Doom'd to Misery's joyless hour.

MR. URBAN, Summerlands, June 2. TO science can be more intimately Nconnected with national prosperity, than that on which Navigation and Commerce indispensably depend; and, therefore, such facilities as the extensive circulation of a work of repute like yours must give to the formation of a true Theory of Magnetic Variation, are manifestly subservient to so essential an object. Further observations and experience enable us to rectify and improve this great subject, in the rapid progress it is making; and with this view I furnished my esteemed friend and the intrepid navigator, Captain Parry, with my conceptions of this infant science, in order that this intelligent character, and the able men about him, might consider my positions, and suggest what might be calculated to advance it to its much wished and ultimate stage.

Some important discoveries recently made relative to the magnetic effects of solar heat, elucidate clearly one curious department of the science of Variation, first noticed by Graham in 1722, and by Canton in 1756, who marked the daily variation, without being enabled to account for it on legitimate grounds. I first observed this description of variation in the southern hemisphere in 1794-5, at Bencoolen, and in 1796 at St. Helena; ascertaining that it moved eastward at the very time when it moved westward in the other hemisphere. If I had made these observations as far south as London is north, I should have found the quantum of diurnal variation similar; and as I stated at the time, it would have been found greater with a needle on the more delicate suspended principle. My account of this interesting phenomenon, printed in our Philosophical Transactions, is referred to as follows, in the proceedings of the French Academy of Science.

"Mr. Macdonald's labours led to two important results. The first (which every philosopher appears to have adopted) is, that the daily variations between the tropics have a sensibly less extent than in Europe. The second (to which less attention has been paid) is, that at the same hours at which in our climate the northern extremity

of the needle moves towards the west, at Fort Marlborough and St. Helena, which are situated to the south of the equator, the movement is directly opposite, namely, to the east.""It is evident that the observations made to the north of the line, of the southern hemisphere present, like agree with those of Europe; and that those those of Mr. Macdonald, a diametrically opposite movement."

1 ascribed these effects on the needle to the action of solar heat on the magnetic poles, rendered weaker or stronger at different times within the twentyfour hours, according to the presence or absence of the Sun: but recent experiments evince that the direct heat of this glorious luminary is the more efficient cause. Professor Morichini has discovered that, when unmagnetised needles were placed for a short time in the violet rays of the spectrum formed by passing the Sun's rays through a prism, polarity was acquired. Consiliachi and Beard tried this experiment withoat succeeding; while the ingenious Mrs. Somerville has rendered her name famous by the manner in which she succeeded, which was by covering the half of her needles with paper, and by placing them in the violet rays of the spectrum given by the prism, the uncovered part became a north pole, and more readily than when the needles were situated in the green, blue, or indigo rays. This philosophical lady covered one half of a needle with paper, and enveloped the other in green ribbon. Thus prepared, and exposed to a strong Sun, it became magnetic, and still more readily, when the Sun's rays were concentrated. She found that a needle half covered with paper, and placed under a blue glass, exposed for some time to a strong Sun, acquired polarity.

Mr. Baumgartner of Vienna polished zones on an oxidised or rusty needle; and after having been placed for some time in the Sun, the polished zones became north poles, and the oxidated or rusty parts south poles. On trying longitudinal polished stripes, no effect was obtained.

To Mr. Christie of Cambridge, magnetic science is much indebted. He has discovered that the oscillations of a magnetic needle stop sooner in the Sun, than in the shade. He found that the oscillations in the same time were fewer in the Sun, than under coHe ascertained, that the higher

ver.

the temperature of the air, the more the magnetic intensity diminished; and by a series of well-conducted experiments, he makes it clearly appear that the solar rays have a magnetic effect, independent of their heat. The Oscillations may be rendered slower or fewer in the Sun, by the expansion of the needle by direct heat; but from the other experiments, it would appear that the diurnal variation is occasioned principally by the direct magnetic action of solar heat. At Port Bowen, the greatest west variation was when the Sun was west from the place; and at Bencoolen and St. He lena, the maximum of east diurnal variation happened when the Sun was situated east from these places. The needle returned slowly to the opposite position, when the Sun ceased to be on the attracting side.

There can be no doubt now, but that the Sun is the great source of magnetic power, communicated to the magnetic poles through the two points on the earth, where the dipping needle will stand perpendicular. The magnetic fluid issues in all directions from these primary points; and thus the nearest extremity of the needle is attracted towards them in the inverse ratio of the square of the distance.

It is earnestly hoped that his Royal Highness the Lord High Admiral will direct the highly important discovery to be made, without which no theory can be established, viz. the real position of each magnetic pole. Supposing the approximated position near the truth, we have a spherical triangle, of which two sides, the colatitude of the pole, the colatitude of London, and the intercepted angle of 100°, being the difference of longitude, are given, to find the angles at the base, one of which ought to be the variation there. This gives the calculated variation equal to 23° 17', less by 1° 13' than 24° 30′, the observed variation. Now the calculated ought to exceed the observed variation, because this last is diminished by the action of the distant south-east pole on the south extremity of the needle at London. All this proves that we have not as yet got the true position of the North-west Pole. It lies not far from Coppermine River; and by obtaining experimentally its position, and the same ten years hence, its path and real rate of movement will be clearly ascertained, and only by such

process. Supposing that the interven tion of ice might prevent arriving at the actual site of the South-east Pole, the oscillations of the needle where progress might be interrupted, compared with the same number of oscillations in the same time on the line of no variation in the other hemisphere, would leave the distance between the place of observation and the supposed "known place of the come-at-able North-west Pole, equal to the distance between the place where the ice stopped progress, and the real place of the Southeast Pole. For reasons stated, the needle would be shaded in both places of observation, and the similarity of atmospheric temperature would be attended to.

It appears that the annual increase or decrease of the variation is unequal. This may arise from the effect of magnetic strata, and more apparently from the situation of the two magnetic poles, relative to the place of observation. From a medium of 396 observations taken by me at Bencoolen in 1794, on a true meridian, the variation was 1° 8' east. In 1822, the Surveyor-general found there a variation of 1° 15′ east. Thus, in 28 years the annual increase has been there only fifteen seconds. In 1794 the North-west Pole was about 37 degrees to the east of the meridian of Bencoolen; and the southeast was 31 degrees to the east of it; and consequently they neutralized nearly the effect of each other, which will be the case for a long period to come; and this accounts also for the very small and slow alteration observable in the variation all over the eastern seas and islands during a long past period. A most important science must continue to float in uncertainty and conjecture, till the rate of movement, the nature of the path, and the positive site of both magnetic Poles shall have been ascertained. I mention both Poles, because some eminent philosophers, seeing anomalies of variation in several places, have placed poles in various situations, in order to ascribe to them such irregularities of variation. This anomaly of variation occurs in the East Indies, in Hudson's Bay, about Cape Horn, among the South Zetland Islands, and remarkably about the Falkland Islands, where Captain Basil Hall, in 1824, found an east variation of twenty-two degrees; while Commodore Byron, in 1764,

made it 23° 30' in that very place; giving only a degree and a half of difference during 60 years. In 1824, the North-west Pole was ten degrees west from Port Egmont at these islands; and supposing no South-east Pole to exist, Captain Hall ought to have found a small west variation. Again, in 1824, the South-east Pole was nearly under the meridian of Port Egmont, and being much nearer than the other, consequently the west variation due to the other Pole ought to appear reduced or neutralized to nearly nothing. To account for this anomaly of 22° east, where in Commodore Byron's time also it ought to have been still farther west, Dr. Halley and Professor Hansteen situate a magnetic pole in the south-west quarter. Captain Cook, in 1774, went within a few degrees of the assigned sites of these poles, and found no indications of their existence. Supposing them, however, to be actually as placed, and to attract the south end of the needle so as to incline the north end into the east variation at Port Egmont, what must become of the undoubted and known attraction of the two poles actually operating? These poles acting as they do, conjointly, would counteract the attraction of the poles of Halley and Hansteen, and, as before, neutralize the twenty-two degrees of east variation to nearly nothing. But still this variation actually appears, and how are we to account for it anong such distracting attractions? It is well known that the magnetic poles within the earth impart magnetism to masses of iron, iron ore, iron bars, &c.; and that such magnetism in each hemisphere is of an opposite quality or name. At Port Egmont the south end of the needle would point to the upper part of a common fire-grate; and the north, to the bottom; while its action would be neutralized at the middle or magnetic equator of the mass of iron. Supposing these islands to be based or founded on metallic ore, or on magnetic strata, it may be consistent with well-known facts to suppose that the magnetic needle is attracted as above; and according as one end may be repelled, or the reverse, on established principles, the local attraction, unaccountable by polar action, as stated, may be accounted for in the manner specified. Navigators call this the attraction of the land, but the descrip

tion which takes place on the plum-' met of a quadrant is not of a magnetic nature; but is referred to matter acting on matter. The shell of the earth is richly stored with metals for the use of man; and of these iron is the most useful. The needle is acted on by metallic substances unequally situated. Where they abound, they acquire polarity; and philosophers imagine poles where the observed effect is due to magnetic strata in many instances. These supposed poles are placed in situations not sanctioned by experience, or any convincing rationale. With the two KNOWN magnetic poles, and with a knowledge of their effect on metallic strata, the variation can be rationally accounted for. It appears that more poles than two would destroy each other's effects, and would embarras calculation, and render it uncertain, if not impossible.

As many have supposed that each magnetic pole has its peculiar magnetic equator, it is necessary to state the real fact of the case, as a component part of the theory as now understood. The true magnetic primary meridian is a circle on the globe, passing through both magnetic poles; and it crosses the terrestrial equator in 91° 30' west, and 86° east longitude. The east and west divisions of this circle will be unequal, because the magnetic poles are not at present at equal distances from the poles of the earth. From the North-west Pole lay off the half of the west division of this primary magnetic meridian, and it will extend to 16° south latitude, in 91° west longitude. From the north-west or southeast pole lay off the half of the east division, and it will terminate in 16° 30′ north latitude, and nearly under the meridian of 86° east longitude. The first of these latitudes will give the farthest south, and the second the farthest north point of the magnetic equator,_common to both magnetic poles. The needle in every part of the primary magnetic meridian will lie in the plane of both magnetic poles, and will have no dip in the above latitudes, being rendered horizontal by the equal attraction of the magnetic poles at equal distances. In every other part of the circle, it will dip towards the nearest pole magnetic. In no other situation, excepting on this magnetic circle, will the needle point, at the same time, to both magnetic

poles. When the nearest magnetic pole is between any place and the nearest terrestrial pole, the meridian passing over that place and these poles, is called the line of no variation to such place; and this meridian continued beyond the terrestrial pole to the magnetic equator on the other side, will be a line of no variation to the inhabitants living under it. On this line the needle will not point exactly to the nearest magnetic pole, because the other end of it is attracted by the more distant magnetic pole in the inverse ratio of the square of the distance; and therefore the observer must move a little to the east or west of the place (according to the position of the more distant magnetic pole), in order that the needle, acted on by both poles, may be in the true line of no variation of such place. Supposing both magnetic poles of equal strength or intensity, two conditions are requisite to render the needle horizontal, or devoid of dip. The first is, that such place must be at an equal distance from both magnetic poles; and the second is, that a line drawn from each magnetic pole to such place, should form nearly an equal angle with its meridian, or with the parallel of latitude, as these angles are complements to each other, to ninety degrees. There are only two places on the terrestrial equator that will include these conditions. The one is at present in 8° east, and the other in 172° west longitude. The magnetic crosses the terrestrial equator at these points, where also of course the needle will be horizontal. If a line be drawn through these points, it will be nearly the present situation of the magnetic equator, which is constantly altering, on account of the perpetual movement of the magnetic poles. The magnetic equator, as at present situated, passes a little to the north of Pharnambooco in Brazil; near to Cape Rocket, to the south of the entrance into the Red Sea; to the south of Goa on the coast of Malabar; to the south of Vizagapatam; to the north of Cambodia; over the south of Manilla; through the Carolinas-Islands; over the equator, as mentioned; and over the north of the Marquesas Islands. In proportion as the magnetic poles move in their orbits within the earth, the points where the magnetic crosses the terrestrial equator will be found more eastward;

as also the extreme points of northing and southing of the magnetic equator. The position of these two places farthest north and south, will be found always by halving the west and east unequal divisions of the primary magnetic meridian passing through the two magnetic poles round the globe.

The ingenious galvanic experiments of Ersted, Ampère, and Arago, evince the existence of east and west magnetic currents occasioned by the Sun in his course; and producing by the action of magnetic caloric heat, the diurnal variation, always greater in summer than in winter. The main magnetic current flows in every direction from pole to pole, diminishing in intensity inversely as the square of the distance, and equal in strength on the magnetic equator, where the currents acting equally on both extremities of the needle, renders it horizontal.

This useful and interesting subject, Mr. Urban, is attracting much attention; and in order to elicit discussion of a new science intimately connected with public welfare, I state from time to time what may tend to advance it gradually to an established theory, on which safety in "the trackless deep so much depends.

Yours, &c.

Mr. UREAN,

JOHN MACDONALD.

June 12. YOUR Saxon readers are much ob

YOUR

liged to you and your Correspondent S. Y. E. for the republication of the Inscription found on the south wall of Leominster Church. Nothing can be more groundless than the objections raised against the authenticity of this Inscription; nor does it require the support of a similar tablet of brass formerly affixed to a column of the Abbey Church at Glastonbury, as noticed by Usher (Antiquitates, p. 9, ed. 1698). The age of the latter is uncertain; and it records an event which, if true, has been so blended with the marvellous and the superstitious, as to throw an air of suspicion over the whole story. The facts recorded in the Leominster Inscription are not of this nature; and whether preserved in brass or stone, or in any other way, is a point of no great importance; but the probability is, that the original inscription being partly decayed, or in danger of destruction, was from its historical importance deemed worthy of being renewed in brass at a later

period. The value of the information contained in it consists in this: that it is contemporary. Of this there is internal evidence. The writer, if we may so call him, speaks in the first person, and gives us the history of his family and property. That family was of the Royal race of MERCIA; and the property comprised most of the ancient fortresses and lands of the Mercian Kings. How much of this property is still vested in those noble families, who are the representatives and descendants of the Saxon Kings of Mercia, his Grace the Duke of Newcastle, who is a lineal descendant of the REMBALDS of CLINTON, may perhaps be capable of ascertaining with the greatest facility, by tracing it either to the Kenelms of Leominster, or to the Rembalds of Clinton, now Clent in Staffordshire. With a view to the elucidation of these points, I have ventured to give you, Mr. Urban, my interpretation of the topography of the inscription, which differs in some instances from that of your Correspondent S. Y. E.

For example, Deorirbynig is there translated Tewkesbury, as if the reading were Deocirbynig; whereas I consider Deotirbynig to be the correct reading, and that Tutbury

in Staffordshire is intended, — not Tewksbury in Gloucestershire. Here we may remark, Mr. Urban, by the way, that in Staffordshire, as well as in Oxfordshire, and other counties, many traces are to be found of the Celtic worship of TEUTATES, and other Aboriginal deities, adopted by our Saxon ancestors also before their conversion to Christianity, which was not effectually and generally completed at so early a period as some would per

suade us. Hence Tutsbury and Tet

bury or Teut's-Bury, Tetsworth or Teut's-Worth, Great and Little Tew, &c. &c. But the further illustration of this curious subject I leave to Mr. Bowles; from whom we may soon expect a considerable addition to our topographical stores, in the Parochial History of Bremhill. At present I shall confine myself to the Leominster Inscription, where the places recorded

I conceive to be these: Chelmsford, Peterborough *, Lichfield, Leicester,

In the original, Medeswelhamstede, the ancient name of the place; before Burgh, Gildenburgh, and Peterborough, were introduced by the love of innovation.

Kenelworth, Clent, Kenilsham, Winchcombe, Hereford, Sutton, Kenchester, Thorney, St. Alban's, Nottingham, Warwick, Gloucester, Stamford, Berkeley, Tutbury, Runcorn, Tamworth, Eddesbury, Sempringham, Lincoln, Cuckamsley, Offchurch, Kingsland, Kenelworth, Clinton (the same with Clent before mentioned), from which place, and not Glympton in Oxfordshire, the noble family of Newcastle takes its name.

I will conclude with some remarks and corrections. For æle read æc, i. e. eac, also, eke; hebbe is understood after poprecan; for nir read nil, "I will not give," &c.; ÿr may be considered an interpolation as explanatory of by; for magopine read ma50pinc.

Yours, &c.

J. I.

DEFENCE OF THE ENGLISH
UNIVERSITIES.

(Concluded from p. 392.)

can certainly with no degree of THE University of Cambridge justice be considered as defective in useful learning. Mathematics have long been considered the best practical system of logic. The art of reasoning is essentially necessary in every department and occurrence of life. The system of education also, which we are vauntingly told "is no suitable preparation for the Church, the Bar, or the Senate," has introduced to both Houses of Parliament some of their most distinguished members, whose lives have been spent in watching public opinions, and in accelerating or stemming the progress of public virtue or public error. The present component

66

members of the University of Cambridge, we are further told, are a Can Granta's elder sons (I forbear to mere pigmy race,-mere algebraists." mention living characters, many of whom would well bear comparison with these,) possibly be deemed a pigmy race in literature or science, whilst she ranks in the number of her literary heroes the names of a Bacon, a Newton, a Milton, a Dryden, a Bentley, or a Porson?

That our Senior Wrangler" was not much more than a inere algebraist, as he identifies himself with the University, we may, upon his own premises, certainly conclude. Having,