Page:Proceedings of the Royal Society of London Vol 4.djvu/158

Rh II. " An Account of the fall of a Meteoric Stone in the Cold Bokkeveld, Cape of Good Hope." By Thomas Maclean, Esq., F.R.S., &c., in a letter to Sir John F. W. Herschel, Bart., V.P.R.S., and communicated by him.

The appearance attending the fall of this aerolite, which happen- ed at half-past nine o'clock in the morning of the 13th of October, 1838, was that of a meteor of a silvery hue, traversing the atmo- sphere, for a distance of about sixty miles, and then exploding with a loud noise, like that from artillery, which was heard over an area of more than seventy miles in diameter ; the air at the time being calm and sultry. The fragments were widely dispersed ; and were at first so soft as to admit of being cut with a knife ; but they after- wards spontaneously hardened. The entire mass of the aerolite is estimated at about five cubic feet.

III. " Chemical Account of the Cold Bokkeveld Meteoric Stone." By Michael Faraday, Esq., D.C.L., F.R.S., &c., in a letter to Sir John F. W. Herschel, Bart., V.P.R.S., &c., and communicated by him.

The stone is stated as being soft, porous, and hygrometric ; having when dry, the specific gravity of 2'94 ; and possessing a very small degree of magnetic power irregularly dispersed through it. One hundred parts of the stone, in its natural state, was found to consist of the following constituents ; namely,

Water 6*5 Alumina 5-22 Sulphur 4-24

Silica 28-9

Protoxide of Iron. ... 33-22

Magnesia 19*2

Lime 1-64

Oxide of Nickel. . '82 Oxide of Chromium "7 Cobalt and Soda. . a trace.

IV. Note respecting a new kind of Sensitive Paper." By Henry Fox Talbot, Esq., F.R.S.

The method of preparing the paper here referred to consists in washing it over with nitrate of silver, then with bromide of potassium, and afterwards again with nitrate of silver ; drying it at the fire after each operation. This paper is very sensitive to the light of the clouds, and even to the feeblest daylight.

The author supplies an omission in his former memoir on photogenic drawing, by mentioning a method he had invented and practised nearly five years ago, of imitating etchings on copper plate, by smearing over a sheet of glass with a solution of resin in turpentine, and blackening it by the smoke of a candle. On this blackened surface a design is made with the point of a needle, the lines of which will of course be transparent, and will be represented by dark lines OB the prepared paper to which it is applied, when exposed to sun- shine. The same principle may be applied to make numerous copies of any writing.

The Society then adjourned over the Easter Recess, to meet again on the 11th of April next.