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ART. XVI. Miscellanea.

I. MECHANICAL SCIENCE.

1. ASTRONOMY, OPTICS, PNEUMATICS, &c.

1. New Comet.

A new comet was discovered at Marseilles on the night of the 26th of December last, by M. Pons, in the constellation of the Swan, near the northern wing. It had a nebulous appearance. Its light was extremely feeble, and its figure indeterminate. It had neither nucleus nor tail. It was seen again on the 29th of the same month, in the evening, but only for a few minutes, in consequence of clouds. Its situation was then about two degrees south of its first observed position. Its light was more bright, and its apparent size increased, A small nucleus could then also be distinguished.

It was seen again on the morning of February 14th, and was still in the constellation of the Swan, but farther south.

The same comet has been observed at Augsbourg on the 2d of this month. It was found near the star i of the fourth magnitude, on the outside of the wing of the Swan, and above the constellation of the Fox. It is considerably enlarged, and its nucleus is now very distinct.

2. New Observatory at Cambridge.

It is proposed to build an observatory within the precincts of Cambridge University, the expense of which is estimated at about 10,000l. A grace will be proposed to the Senate for a donation of 5,000l. from the University chest, and a subscription opened for raising the remainder of the sum. Application is to be made to Government to appoint an observer and an assistant, with adequate salaries.

3. Supposed Transit of a Comet.

Mr. Capel Loft, in a Letter to the Editor of the Monthly Magazine, describes a body passing over the sun's disc, which he supposes may have been a comet.

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I saw it about 11 A. M. (on the 6th of Jan.) with my own

reflector, with a power of about 80; with an excellent Cassegrain reflector made by Crickmore of this town, with about 260; and with a reflector of Mr. Acton's, with about 170.

"It appeared when I first saw it, somewhat about one third from the eastern limb; subelliptic, small, uniformly opaque.

"About 24 hours P. M. it appeared to Mr. Acton considerably advanced, and a little west of the sun's centre, and I think it appeared then 6 or 8 seconds in diameter. I had been able to see no spot on the 4th, nor again on the 8th; and even on the 6th Mr. Crickmore could not see it a little before sunset, though the telescope already mentioned gave him every advantage.

"Its apparent path while visible seemed to make a small angle with the sun's equator. Its state of motion seemed inconsistent with that of the solar rotation, and both in figure, density, and regularity of path, it seemed utterly unlike floating scoria. In short, its progress over the sun's disc seems to have exceeded that of Venus in transit.

There are two instances, if not three, of comets seen in transit, and this phenomenon seems to have been one. I wish it may have been seen elsewhere."

Ipswich, Jan. 10.

4. New Photometer.

Mr. Horner of Zurich has invented a photometer which, for its simplicity of construction and facility of use, deserves to be made known. An account of it has been published in the Bibliothèque Universelle, from which this extract is made. It consists of a pasteboard tube an inch and half in diameter, and four inches long. A flat ring of much larger diameter surrounds it a short distance from one end, and an opening is made in the ring, by which slides can be made to traverse through and across the tube. The opposite end of the tube is cut into a form which will fit round the eye and exclude extraneous light when the instrument is used, and within it is a convex lens of two inches focus, which renders the diaphragms that are passed through the ring perfectly distinct.

The scale of the instrument is constructed on the same principle with that described by M. Lampadius, and consists of

a number of similar diaphanous discs, which are added together at the outer end of the tube until they intercept all light, and the number necessary for this purpose indicates the intensity. The units or degrees of M. Horner's scale are discs of very fine, thin China paper, covered with oil varnish on each sur

A thin plate of metal, wood, or other substance, capable of being passed through the orifice in the ring is perforated with 10 round holes, the first of these is left open, and the others are covered by the discs of paper from 1 to 9 progressively, each being properly numbered. These supply the units in observation, and the tens are made by putting together 10, 20, or 30 discs, pressing them close and connecting them into one mass by an edge of very fine paper pasted on.

In using the instrument, the eye being applied to its proper end, the other is directed towards the light to be measured, and then one or more bundles of the tens are introduced, according as the light is more or less brilliant, at the object end of the tube, and pressed together by a small ring or short tube introduced after them; then, by passing the slider with the units across the tube till the light is entirely excluded, the number of discs necessary is ascertained, and the light estimated accordingly.

To make the instrument more sensible, it is proposed that an object glass of some inches focus be fixed at the outer end of the instrument.

The fixed point of the photometer has been made after M. Lampadius, the light of phosphorus when burning in oxygen gas, and if any alteration occur in the state of the discs, it is rectified by comparison with this point.

The following are some observations made with this instrument :

Light of the sun at an elevation of 30°, sky

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75 degrees.

70

56

49

53

Light of a full moon

-moon 5 days old

-from snow enlightened by the sun
-from snow in the shade

-starry sky, (14 March, 1817)

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-sky clear of stars, (14 March, 1817) 4.5 -planet Venus at an elevation of 30° 9 (5 April, 1817)

constellation of Orion, (14 March, 1817) 7 -of a common candle 2 feet distant

5. New Barometer.

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A new barometer has lately been invented by Mr. Adie of Dumfries. It is described as being more portable than the common barometer, and less liable to accident. The moveable column is oil enclosing in a tube a portion of nitrogen, which changes its bulk according to the density of the atmosphere. This is something like the common air thermometer,

6. New Musical Instrument.

M. Marstrand of Copenhagen, celebrated for his mechanical inventions, is said to have invented a new musical instrument called the Harpinella. It is in the form of a lyre, is smaller than the common guitar, and yet equal in tone to the harp. By a very simple piece of mechanism, the semitones are made with the same facility and precision as on the pedal harp.

7. M. de Lalande's Medal.

The gold medal founded by the late M. de Lalande has been awarded by the Institute and Royal Academy of Sciences at Paris, to Mr. Pond the Astronomer Royal, at Greenwich, for his interesting and important researches on the annual parallax of the fixed stars.

§ 2. ARCHITECTURE, NAVIGATION, THE ARTS, &c.
1. Plymouth Breakwater.

The breakwater at Plymouth has withstood the late gales in an almost unexpected manner; the only thing which gave way was a crane, that could be replaced in a few hours.

At the commencement of the winter a few large stones were placed by themselves on the top or finished part of the breakwater, to ascertain how far they would withstand the

winter gales, they stood all but that which occurred the begin ning of this month; it moved them, and they were found lying on the north slope. There were three of them, one of nine tons and the other two of five tons each; they are to be replaced for further trial.

2. Moveable Axletree.

Mr. Ackerman of the Strand has lately introduced a considerable alteration into the axletree of carriages. The improvement, it is said, will allow the carriage to be built 18 inches shorter; the body to be hung lower, and the fore wheels to be made larger. The vehicle will turn in much less space than carriages of the common construction, and is more difficult to overset. Several coachmakers are constructing carriages upon this new plan.

3. New Harpoon.

A new Harpoon has been invented by Mr. Robert Garbutt, of Kingston upon Hull for the Greenland fishery; calculated to secure the whale in the event of the shank of the instrument breaking. The improvement consists in placing a kind of preventer made fast to the eye of a foregager, which passing along the shank of the harpoon, is attached to the thick part of it in such a manner as neither to lessen its strength nor impede its entrance when the fish is struck.

4. Harpoon Guns.

Some of the Leith whale ships are furnished with harpoon guns for this year's service. The gun is mounted on the bow of the boat, and the harpoon with the line attached is fired out of it, and will strike at the point blank distance of 20 or 30 fathoms; by which means a fish may be struck when there is no chance of reaching it by throwing the dart with the hand. They have been used by the Hull vessels for several years.

5. Nautical Instrument.

Among other ingenious inventions submitted to the Board of Longitude, one countenanced by the Board and recommended to the Lords of Admiralty for immediate trial, is likely to facilitate the object intended in exploring the polar regions. The merit of this invention is, that it works horizontally and

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