an inch; the Comrie House one was inclined to the north half an inch. The severest shock was at ten minutes to twelve, the next a quarter past two, and the third at half-past four. The first, I have marked in the register, 5; the second, 3; and the third, 1. No damage that I have heard of has been done. The weather, for the two preceding days, was remarkably wet and close, much resembling that in which the shocks occurred in 1839,-so much so was the sky the evening previous, that I was remarking to some folks, that it looked very like an earthquake night. But I have more than once observed the same misty and lurid sky, without any shock, so that, after all, the thing may be a mere coincidence."

12th September 1841.-On the day here mentioned, a phenomenon occurred on the south coast of IRELAND, which was most probably caused by an earthquake in the ocean. The account to be now given, is extracted from a paragraph published at the time in a Wexford newspaper. It is interesting to observe that the sea retired in the first instance,-just as happened on the occasion of the Lisbon earthquakes in 1755 and 1761, and that a few minutes before the reflux of the sea, there were "a number of short, loud, but rather smothered reports like cannons." It is not difficult to understand how submarine eruptions should produce, where they occurred, a momentary elevation of the sea, whereby the waters would be drawn from all the adjoining parts. The reports which occurred simultaneously with these eruptions, are strongly corroborative of the electrical theory.

Singular reflux in the Sea.-Sunday, the 12th (September 1841) inst. was a misty dark day, with wind S.SW. to S. About noon, the low growl of distant thunder was heard, and the wind lulled, which rendered the fog more dense. At Kilmore, ten miles south of Wexford, and directly opposite the Saltee Islands, the attention of the inhabitants was attracted about noon-time, to a number of short, loud, but rather smothered reports, like cannons, and it was supposed that they proceeded from some ship bewildered by the fog. The tide had flowed pretty well at the time, and the fishing boats in the pier were all afloat, when, in the space of two or three

minutes, the water receded from the pier, and some walked dryshod where that short space before the boats had been floating in five or six feet water. In the course of a few minutes the waters began to return, much in same way as they had receded, and the tide continued to rise for the usual time. There was no extraordinary commotion, only an increased surf. After repeated rolls of thunder, and some heavy showers, the sky cleared up. It is the belief generally that this singular motion was the effect of an earthquake, whose shocks have of late been so frequently experienced in Scotland."

26th November 1841.-That this shock was pretty severe, is proved by extracts from the following letters.

At COMRIE, it was felt, as the Rev. Mr M'Kenzie (then minister of the parish) wrote,-" About 12 40 both the sound and the shook were very distinct; the former very like the sound that would be occasioned by a carriage passing along the street, with great rapidity; the latter causing the house to shake three times as much as a carriage would have done." At DUNIRA, as Sir David Dundas wrote,-"A shock was felt about 1h 15 P.M., accompanied with a noise, evidently proceeding from NE. to SW. The day before had been very wet and rainy; but during the night it cleared up to hard frost. Some snow, but not to any depth, had fallen during the early part of the morning. A sharp frost succeeded, and at the time the shock took place, it was freezing hard. I was shooting at the time, with an English gentleman, who told me, that he observed the trees shake in a very peculiar way, and that it was very much the same sort of thing that he had felt in Rannoch, on the night of the 23d October.

20th December 1841.-At KINTAIL, in Ross-shire, a severe shock occurred at 4 P.M., which greatly alarmed the inhabitants of several parishes. "There was nothing peculiar in the state of the weather, or the appearance of the day, unless it might be a stillness and calmness in the atmosphere, which, although remarked at the time, is not uncommon at even this season of the year. There was no recurrence of the shock. The noise which invariably accompanies such visitations, like the rushing of water or the rattling of a carriage,

was very distinct. We have before noticed the extreme prevalence of lightning, with occasional thunder, in the west and north Highlands, this winter; but the above is the only case of earthquake in the same districts which has come to our knowledge."

A few remarks may here be offered in regard to the most material inferences from the foregoing notices of shocks in 1840 and 1841:

(1.) That there was a movement of the earth's surface, seems proved by the facts stated under dates 10th and 22d March 1841, and 26th and 30th July 1841. These indicate that the ground was moved, not merely horizontally, but also vertically from its previous position, to which, however, it immediately returned. An undulation of the ground was in fact produced.

(2.) That in the Comrie district, these shocks emanated from a point situated a little to the west of the Melville Monument. At Comrie, Clathick, and Crieff, the shocks on 18th January, 7th April, 26th and 30th July 1840, were respectively perceived to come from the west. At Dalchonzie, the shock of 30th July was felt and seen to come from the north, sloping upwards. At Dunira, the shocks on 30th July 1840 and 26th November 1841, came from the NE. In Argyleshire, the shock of 30th July 1840 came from the east, whilst at Aberfeldy, it came from the SW. Any person acquainted with the relative situation of these places, or who studies them on a map, will perceive that the shocks felt at them, must have emanated from the point just indicated.

(3.) That in most cases, atmospherical phenomena accompanied the shocks.

Explosions, or crackling sounds in the air, are related under dates 8th January 1840, 21st April and 12th September 1841. This phenomenon is the more remarkable, as the reports were, on the last of these occasions, heard at sea, and were mistaken for the firing of cannon, so that they could not be confounded with the subterranean noise, which also accompanies the shocks.

Several of the shocks took place in violent hurricanes or storms, as is shewn under dates 18th January and 15th September 1840.

Having thus noticed all the shocks of any severity which are known to have occurred in Great Britain, during the years 1839, 1840, and 1841, it may not be uninteresting to record briefly the shocks felt during the same period in other parts of the world. Data will thus be afforded for ascertaining (1.) Whether the shocks in this country occur at or about the same time as those in foreign countries,—an opinion very generally entertained; and (2.) Whether the shocks in this country, present the same general features as those in foreign countries.

On Cutting Half-Round, and other Curved-Faced Files. By the late Sir JOHN ROBISON, K.H., F.R.S.E., F.R.S.S.A. (Communicated by the Royal Scottish Society of Arts.)†

It is well known to workmen that, although it be an easy matter to get flat-faced files of almost any required degree of smoothness and regularity of surface, a half-round file having an approach to such smoothness or regularity is altogether unattainable at any cost.

A method having occurred to me of striking half-round or even round files with the same smoothness, and with nearly the same accuracy of figure, as the flat files, I beg leave to submit the process to the Society, that it may, through these means, become known to those to whom it may be of use.

To form a half-round file, either convex or concave, I pro

* Mr Maclaren of Edinburgh has supported this view. Thus, with reference to the earthquake at Zante, on the 30th October 1840, he observes, "Here we have again a remarkable example of the coincident occurrence of earthquakes in distant parts of the world. The town of Zante has been ruined by a series of terrific shocks between the 24th and 30th October; and our paper of 31st October records a shock on the 26th of that month at Comrie. The distance between these localities is nearly 1700 miles. The bearing is SE, and NW. It may be remembered, that the great earthquake of 23d October 1839, was felt simultaneously at Comrie, in Piedmont, and at Reggio in Calabria,—that is, over a line coinciding in direction with the present, and only a little shorter. If we prolong the line connecting Reggio and Comrie, farther north, it strikes Mount Hecla, and may thus be said to have an active volcano at each extremity-Etna at the one and Hecla at the other. It is extremely probable, that we shall hear of earthquakes, between the 24th and 30th October, in the Alps or Apennines, or at other intermediate localities."-(Scotsman of December 1840.)

+ Read before the Society, 12th December 1842.

pose that blanks should be prepared as if for thin equallingfiles (i.e. of uniform thickness and breadth throughout), and that they should be struck on one or both faces, of the degree of fineness required. This having been done, I propose that, by means of a screw-press and swages of copper, or other soft metal, they should have the required degree of curvature impressed on them before being hardened, and that, in this manner, files with curved faces, but with the teeth of equable depth all across them, should be obtained.

In a similar manner I propose to form three-quarters round, or even cylindric, smooth files, by cutting flat blanks on one face, and then bending them on steel mandrils into a tubular form previous to hardening them.

On communicating this plan to the eminent manufacturer Mr Stubbs of Warrington, I learned from him that something of this kind had been attempted by his house, but abandoned on account of the difficulty experienced in getting the files into the curved shape after they were struck. Mr Stubbs at the same time sent me a file so made, thirty years before. This file at once explained how the difficulty had arisen, as, instead of the blank having been made of uniform thickness and breadth, it has been fashioned like an ordinary crossing file, and therefore not susceptible of being squeezed into the regular curved shape by simple pressure. If Mr Stubbs had thought of making the flat blank, he would no doubt have succeeded better; and the formation of tubular files, which he acknowledges never occurred to him, must have followed the other at a short interval.

EDINBURGH, November 14, 1842.

REPORT OF COMMITTEE.

Agreeably to the remit made to us by the Royal Scottish Society of Arts, of date the 13th December last, on a paper read by Sir John Robison, K.H., on cutting and manufacturing half-round and round files,— your Committee beg to report, that they have also had remitted to them three half-round pillar files, manufactured by Messrs Johnson, Cammell, & Co., Sheffield, which were exhibited at the Society's meeting, on the 23d instant, made in the manner suggested by Sir John. Two of these files were cut on the convex side only, and the other on the concave side also, and appear to your Committee to be very fair specimens as a first trial, although they are not so straight, and of so uniform curvature, as might be required.