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cumstanced, is remarkable), the latter furnished +22°.4; and, lastly, when (B), in the position of Fig. 12, indicated a rate of +8.7, the time-keeper (C) gave a result of -8.2. In a subsequent set of experiments, the chronometer (C) was successively applied to the south pole of the same magnet. The results are recorded in the following comparative Table, the
time-keeper (B) being at the same time applied to the opposite pole.
In each of the preceding examples, it will be observed that the accelerations in the rate took place when the magnetic power was transmitted through the centre of the balance; and the retardations, when it passed through the middle of the main spring. These results are the reverse of those recorded with respect to chronometers (B) and (C). In the pursuit of experimental science, every result ought to be fairly and impartially recorded. The admirable maxim of Bacon, we cannot controul nature, unless by making her manifest, should ever be present to the mind of the inquirer.
As an example of the comparative effects of the poles and equator of a circular magnetic plate, one of this form, 8 inches in diameter, and a quarter of an inch thick, was selected, and three chronometers (B), (D), (E) respectively applied to the parts here alluded to, as particularly represented in Fig. 13. The north pole of the plate is denoted by N, and when the time-keeper (B) was applied to it, so that its balance might be as near as possible to the pole, its detached rate of – 8”.1 was changed into +2".2; but, on afterwards applying the same part of the chronometer to the south pole, the gain, instead of being 10".3, as observed in its former situation, was only 1".9. In like manner, on placing the chronometer (E), with its ba
lance as near as possible to the south pole of the plate, its detached rate of +8".5 was increased to + 27".2; and, on detaching the chronometer from the magnet, the rate returned to +8".3, being only 0".2 less than its former detached rate; and which, considering the powerful influence the time-keeper had been subject to, by the action of the magnet, was in some degree remarkable. By afterwards placing the same chronometer on the plate, so that the centre of its bottom should coincide with the middle of the magnet, and that a radial line proceeding from the centre of the chronometer through the axis of the balance might be at right angles with the axis of the magnet, the rate declined from + 8.3 to —2”.6; so that the south pole of the magnet produced an increment of + 19.0 in the rate, and its equator a decrement of 10".9. So also, when the centre of the chronometer (D) was placed over the middle of the magnetized plate, and the radial line before alluded to was perpendicular to the axis of the magnet, the detached rate of +2".0 was increased to +3". 1. On removing the chronometer, this rate declined to 0".9; but, on applying the machine to the north pole of the plate, the last mentioned rate was augmented to +3".1, being the same as that produced when the time-keeper was applied to the equator of the plate; but the actual increment in the latter case was 2".2, whereas in the former it was only 1".1; a necessary effect of the superior energy of the pole of the plate. The great effect of the middle of the plate on the rates of the chronometer, will not be regarded as remarkable, when it is considered that only a single point of the chronometer could be applied to the equator of the magnet; and that both the balance and the main spring, were in each case beyond the centre of the plate, and consequently under the influence of an attractive force, less powerful than that developed by the poles of the magnet, but much superior to the effect of the actual equator of the plate.
One thing worthy of observation in these experiments is, the immediate influence which the magnet exercised on the chronometers, and likewise the freedom with which they lost the magnetic power, when the attractive influence was less energetically developed, either from a change in the position of the instrument, or from its being detached from the magnet altogether. This circumstance, taken in conjunction with some other phenomena which I have lately noticed, would seem to countenance the opinion, that the influence of magnetism is sometimes only of a temporary kind; and that a chronometer frequently returns to its original rate, as soon as the exciting cause is removed. In a great number of instances, I have found the change of rate to have been immediate, both from a considerable gaining rate to one of a great diminution; and, on the contrary, from a great decrement to a large increment. It would be an interesting question to determine, if the sea and land rates of chronometers are, in the generality of cases, immediately acquired. From the few observations which I have had an opportunity of making, this would seem to be the case; and Mr Fisher, in his in
teresting paper in the Philosophical Transactions for 1820, seems almost to countenance the idea.
PLYMoUTH, October 10, 1823.
ART. II-Description of the Whirlwind at Scarborough on the 24th June 1823. By John DUNN, Esq. Fellow of the
Royal College of Surgeons, London. Communicated by the Author.
THE extraordinary, and to many even alarming, meteoric phenomenon which occurred at Scarborough in the afternoon of the 24th of June, induced me to make every exertion in collecting such facts respecting it as could be depended upon. The various conflicting accounts which I received from above twenty witnesses, have been carefully balanced together; and although I had only the good fortune to observe its effects, yet the materials I now present to you will, I trust, be found tolerably accurate. After a fortnight of very boisterous, and, for this period of the year, extremely cold weather, the wind having kept steadily to the N. and NE., and the thermometer as low as 53° Fahr., a thunder-storm burst from the west at a little before 3 in the afternoon. One of the reports was very loud, and awfully grand; the lightning, however, did no mischief, and the rain was soon over. After the expiration of ten or fifteen minutes, and during the calm which supervened, some persons sitting on the lofts of a manufactory on the sands were struck with the singular appearance of the clouds. They remarked a heavy cloud, descending from the SW., and a lower one. Scudding from the NE., attract and strike each other with greatenergy, the surrounding clouds rushing in a whirl to the same centre, and then rebounding. This scene of elementary confusion instantly arrested the notice of all the workmen. The whole mass of clouds was observed to be in violent agitation; an upper dense and dark stratum seemed to be pressing a lighter one down to the earth. They were then blended in one dense column, which descended to the ground, passed from the field of Mr Tindall in a direction from the W.N.W., over the hedge which forms one of the boundaries of the plantation walk. Its force was here so great, that it levelled two very fine elms of about four feet in girth, one being torn up by the roots, and the other broken off at the surface of the ground. The thorns and some intervening trees escaped unhurt, although a considerable fissure was observed in the ground, which must have been occasioned by the disturbance of the roots from the impetuosity of the wind. The space between the two fallen trees, according to my measurement, was 28 paces, which, I conceive, will give some idea of the extent at that time of the lower portion of the whirlwind; for the trees having fallen across the walk, it must have struck parallel with the fence. It now passed across the young plantation on the other side, shook the trees most violently, but did no farther mischief than breaking off the summit of one of them, which I attribute to the great elastic power of these young trees, and the less surface of resistance which their branches would present. The cloud continued its march in majestic grandeur across the road, passed some labourers at the waterfall below the terrace, tore up some cabbage-plants in a garden on the left, went over Ramsdale height to the sands, drove a machine containing a camera obscura into the sea, and dashed it into a hundred pieces. It now made a direct course to the east, scattering the sand to the height of 60 feet, which almost blinded a person who was running from the precarious shelter
he sought in a bathing machine; the whole line of these carriages was turned over upon their broadside, and the tide being up, they were driven into the sea, some without their roofs or wheels. The scene became now highly animated and impressive. The pedestrians on the pier, with that energy inspired by fear and the approach of danger, were seen making their escape as they could. Some of my acquaintances enjoying their wine in a cabin of one of the vessels between the piers, were suddenly alarmed by the boy rushing down from the deck, and crying out “The bathing-machines are running into the sea, many have turned over, and some heels-over-head.” Their vessel in an instant broke its anchorage, and turned over on its beam ends, to the no small destruction of their glasses and Falernian. The tornado being now between the piers, having passed over a considerable surface of the tide, had driven the water in foam and spray to the height of the ship's topmast. After making much havoc among the light boats, raising one 8 or 10 feet out of the sea, staving, upsetting, and filling others with water,turning the brig just mentioned upon its beam ends, and which but for the pier would have been upset, and forcing three other vessels from their moorings, it passed through the harbour, drove round, with great velocity, a large crane, and, carrying away a basket, an umbrella, and other light bodies, was at length broken by a heap of timber, and rising over the battery in rapid volu- . tions, whirled into the clouds and disappeared. Your inquiries in a former Number (No. IX. p. 41.) on these phenomena, I shall now endeavour to answer to the best of my means of information. From the immense quantity of water and foam scattered about, and from the violent agitation of the waves beneath, many experienced seamen had deemed it a water-spout. It left no trace of water, however, when it first passed over the land, but seemed a dense column of vapour, performing very rapid and violent revolutions around its axis. The sea was evidently taken up by the energy of the rotatory motion of the winds: its surface was not at all agitated till the column passed over it, and the water carried up was not in a solid cone, which it would have been had there been a vacuum, but in spray and foam. The persons who saw the water-fall have no doubt it was from the sea, and are persuaded, from the im