368 Royal Society. 



Subjoined to the above paper is a letter from the author to Sir 

 John Herschel, containing a statement of comparative observations^ 

 made with a mountain barometer, and with the compensation baro- 

 meter, from which it apj)ears that the use of the latter is attended 

 \vith the saving of a great quantity of troublesome calculation. The 

 comparative observations are given in a table, exhibiting a range of 

 differences from +"01 2 to —•016 of an inch. 



II. " An Account of the fall of a Meteoric Stone in the Cold 

 Bokkeveld, Cape of Good Hope." By Thomas Maclear, 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 jjossessing 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 Lime 1-64 



Silica 28-9 Oxide of Nickel. . -82 



Protoxide of Iron. .. . 33'22 Oxide of Chromium "7 

 Magnesia 19*2 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 potas- 

 sium, 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 photo- 

 genic drawing, by mentioning a method he had invented and prac- 

 tised 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 sur- 

 face a design is made with the point of a needle, the lines of which 



' Some further information respecting this fall of meteorites will be 

 found in the Intelligence and Miscellaneous Articles in the present Num- 

 ber, p. 391.— E. W. B. 



