The great circle, which passes through Regulus and Spica Scorpio. Virginis, is nearly the same with the ecliptic, and if it be produced to the eastward, it meets the Scorpion, a remarkable constellation on account of the four stars in its head, which form a large arch from N. to S. round Antares, or the Antares. Cor Scorpionis, which is placed as a centre to them. One of the four stars is of the 2d magnitude, and Antares is a bright star of the first magnitude.

The Balance contains two stars of the second magnitude, Libra. which form the two scales: the line which connects them is nearly perpendicular to that which may be drawn from Arcturus to Antares, and they lie a little to the south of the middle of this line of direction. The southern scale is situated between Spica Virginis and Antares, and these three stars are all very nearly in the ecliptic. Spica Virginis is at the distance of 21°, and Antares at the distance of 25°, from the southern scale.

Sagittarius is a constellation, which follows the Scorpion, Sagittarius. being a little to the east of it. It is in the line, which, passing through Spica Virginis and Antares, follows nearly the direction of the ecliptic: it contains several stars of the third magnitude, which form a large trapezium, two stars of which, together with two others, form a second trapezium, perpendicular as it were to the first. Sagittarius may be known by a line drawn through the middle of the Swan and Eagle: for it is 35° south of the Eagle, or nearly the same distance from it as the Eagle is from the Swan. Sagittarius may also be known by the diagonal drawn from the head of Andromeda to a Pegasi, the same line, which produced towards the north points out the belt of Perseus.

The line drawn from Antares to the pole star passes through Ophiucus and Ophiucus, or Serpentarius, and then through Hercules. It Hercules. is rather difficult to know these constellations, and therefore they must be described more particularly. The line drawn from Antares to the Lyre passes near the head of Ophiucus, which is not far from that of Hercules, and lies to the southeast of it. They are marked by two stars of the second magnitude, and the line which connects them points to the Crown; it also passes through y Herculis at the distance of 13° from the head of Hercules. Herculis is at the distance

of

Ophiucus and of 3° to the north-east of y, the line drawn from it to y Hercules. points on the north to Herculis, and on the south, or rather south-west, to a Serpentis, which forms nearly an equilateral triangle with the head of Hercules and the Crown. The line drawn from the head of Ophiucus to the southern scale of the Balance passes through and Ophiuci, two stars of the third and fourth magnitudes, which are at the distance of only 1° 20' from one another, and in the line drawn perpendicular to that which was last described. ♪ lies to the north-west of, and these two stars point on the south-east towards in the western knee of Ophiucus, which is 72° from . This same direction will lead near to », the star in the other knee of Ophiucus, which is about 9° to the south east of . These same stars ♪ and point a little below a Serpentis, and, if considered as one group, they would make nearly an equilateral triangle with a Serpentis and 8 in the northern scale, 44° north-west of a Serpentis is d, and 3° south-east is of the same constellation. The direction of these three stars is also towards and Ophiuci, which are 11° from Serpentis. B and y, the two stars in the eastern shoulder of Ophiucus, are in the line drawn from the head of Hercules to the head of Sagittarius: this line passes a little to the south-east of the head of Ophiucus. Bis 8° and y 11° from the head of Ophiucus. A line drawn through them would pass between the two heads of Hercules and Ophiucus: the line connecting these two heads points to at the extremity of the tail of the Serpent, which is 22° east of the head of Ophiucus. The Jine drawn from the most eastern stars in the Crown (which are on the side turned towards the Lyre) to a Serpentis passes by the head of the Serpent, between y and ß, two stars of the third magnitude: B is the more western of the two. The western foot of Ophiucus lies between Antares and B, the northern star in the head of the Scorpion : the eastern leg is between Antares and Sagittarii, which is the highest and most western star in the bow.

Capricorn.

.

Capricorn may be found by producing the line drawn from the Lyre to the Eagle: this line will pass through a and two stars of the third magnitude in the head of Capricorn. These stars are only 2° from one another. Farther

7

to the east by 20° are two other stars, and ♪, situated east and west about 2° asunder: they are in the tail of Capricorn. Fomalhaut, or the mouth of the southern Fish, is a star of Fomalhaut. the first magnitude, and is pointed out by a line drawn from

Aquila to the tail of Capricorn. Fomalhaut lies about 20°

The Dolphin is a small constellation situated about 15° Delphinus east of the Eagle. It consists of a lozenge of four stars of the 3d magnitude. A line drawn from the Dolphin perpendicularly through the middle of y, a, and 8, the three stars in the Eagle, will pass through in the extremity of the tail of the Serpent.

Aquarius is found by a line drawn from the Lyre through Aquarius the Dolphin, and carried on about 30°, which is as far beyond the Dolphin as the Dolphin is distant from the Lyre: Aquarius lies a little to the east of this line. A line drawn from the Dolphin to Fomalhaut will pass entirely across the constellation of Aquarius, and it will pass about midway between and 8, two stars of the 3d magnitude, in the shoulders of Aquarius. They are the most remarkable stars in the whole constellation, and are about 10° distant from one another.

The Whale is a large constellation, situated on the south Cous. of Aries, and extending through a space, which is equal in length to the distance of the Pleiades from the four stars in Pegasus. A line drawn from the girdle of Andromeda, and passing between the two stars in Aries, will meet a, a star in the mouth of the Whale, which is of the 3d magnitude, and 25° from the horns of Aries. A line drawn from Capella through the Pleiades will also pass south of a Ceti. A line drawn from Aldebaran through the mouth of the Whale will pass through B, a star of the 2d magnitude in the tail: is 42° west of ɑ, and very near the coustellation of Aquarius. The square in Pegasus is alone sufficient to point out the Whale; for the line drawn through the two most southern of these stars passes between Aries and the knot of the Fishes, and will meet the head of the Whale: and the line drawn through the most eastern stars in the same square points to the tail, Between the head and the tail are situated y and, and between and the tail is o, a changeable

star,

Zine might be supposed easily oxidable.

possessed by that metal, though I could fully speak to the facility with which it could be worked into vessels, and of its application to other purposes. I was still, for want of longer experience, not decided as to its changeability when exposed to the action of water and air.

From the great affinity which zine possesses for oxigen, it might be expected to oxidate with great avidity, and on that account be rendered useless in the situations above alluded But it is not, to; but, to the astonishment of most theorists, the contrary proves to be the case. Many specimens of zinc, both in the state of sheets and wire, have been exposed in the open air, as well as in damp rooms, without undergoing any other change than that of colour. Indeed it appears, that a piece of polished zinc will lose its lustre, and assume a blue gray colour, when exposed in a damp room for the space of a few weeks. An oxide is formed upon the surface, which, though of an imperceptible thickness, is so exceedingly hard, and at the same time so insoluble, that it resists all the future atLess affected tacks both of the air and of water. From numerous expethan copper by riments I have ascertained, that copper is much more able to waste than zinc in sea water, and even in strong solutions of muriate of soda. There cannot be therefore a doubt of its ready application to the sheathing of ships.

except superhcially.

seawater,

Its superiority

over lead or

For the purposes of roofing houses, forming cisterns, copper for va- pumps, pipes, &c., it possesses many advantages over lead rious purposes, and copper. In the first place it is equally durable with those metals, without possessing any of their deleterious effects. It is also capable of being lapped and soldered with the same facility as sheets of copper, lead, or tinned iron plates; and may be worked to advantage equally by the brazier, the plumber, and the tinman. Its little specific gravity, which is to that of lead as 7 to 11, compared with its greater strength, which is 15 times that of lead, gives it a decided advantage over that metal in point of price. Allowing the sheets of zinc to be only th the thickness of lead, the zinc will come in at one third the price of that metal. Its advantage in a similar point of view over copper will not admit of a question.

General size of the sheets.

The sheets are generally made 2 feet by 4, and can be rolled as thin as 6 ounces to the square foot.

Sheets

Sheets or wire of zinc George of Bristol, or of

may be purchased of Mr. Philip Messrs. Harvy and Golden, 98, Houndsditch, London: Of whom may alsó be had, vessels and utensils of any form. They likewise undertake the roofing of houses, or sheathing vessels, with zinc.

By giving the above a place in your much esteemed Journal, you will much oblige

Your obedient servant,

CHARLES SYLVESTER.

P.S. I observed some time ago in your Journal, experiments by Mr. Davy on the subject of the production of the muriatic acid and fixed alkali by galvanism, in which some of my former experiments were alluded to. I do not think Mr. Davy is decisive on the subject, and have not a doubt of very soon confirming all that I have previously asserted.

Sheffield, Nov. 20, 1807.

III.

Description of Mr. Davis's improved Machine for Painters and Glaziers".

THE frequent accidents which happen to painters and Machine for

glaziers, from the unsteadiness of their machines, and the preventing accidents to pain: consequent misery brought upon their families, stimulated ters and gla Mr. Joseph Davis, of the Crescent, Kingsland Road, to en- ziers. deavour at their improvement. The result was the machine delineated in plate I, which may be made perfectly firm and secure, without occasioning any injury to the wainscoting or paint. In those cases however, where the bottoms of the windows are flush with the floor, as is usual in the best apartments of modern houses, neither the common machine, nor this with the improvement intended for general use, can be applied: but Mr. Davis has contrived an additional piece to be used on such occasions, which renders it equally secure.

• From the Trans. of the Society of Arts for 1806, p. 138.