344 Analysis of Scientific Books and Memoirs. 



The malt must be first macerated in water nearly boiling, to obtain its 

 soluble particles. The plaster and lamp black are then mixed in a basin 

 with that liquid, and when it is evaporated to the consistency of paste, the 

 olive oil is mixed with it. and a little oil of lemons or lavender is added 

 to perfume it. In place of plaster, an equal quantity of common potter's 

 clay may be used. 



9. Mr Jennings Improved Gas Burner. 

 This ingenious contrivance, the object of which is to close the passage 

 for the gas, even if the stop-cock has been heedlessly left open, and there- 

 by prevent all smell, and all risk of forming an explosive mixture, is shown 

 in section in Fig. 12, Plate VIII. The gas rises up the passage a of 

 the socket cc, and is prevented from passing into the burner by the ball b, 

 which shuts the passage. In order to allow the gas to pass, the burner is 

 lifted up by the hand, which raises the ball b out of its place, and the gas 

 passes from a into d, and up the tubes ee. When the gas has burned about 

 a quarter of a minute, the pin f becomes hot, and the heat is conveyed to 

 the bent arm g, which will curl up, as shewn by dotted lines, in conse- 

 quence of the different expansions of the two dissimilar metals of brass 

 and steel, of which it is made. The ball being thus drawn aside from its 

 seat, the burner may be let down from its raised position, and the gas will 

 continue to flow. When the flame is extinguished, the pin f and the 

 bent arm g become cold, and the uncurling of the latter brings the ball 

 into its seat and closes the passage for the gas, even if the cock has been 

 incompletely shut, or afterwards carelessly opened. — See Newton's Journal 

 of the Arts, vol. ix. p. 179. 



Art. XXXII.— ANALYSIS OF SCIENTIFIC BOOKS AND 



MEMOIRS. 



I. Descrijition of a Monochromatic Lamp, with Remarks on the Absorp- 

 tion of the Prismatic Rays by Coloured Media. By David Brewster, 

 LL.D. F. R.S. Lond. and Sec. R. S. Ed. &c. 



. On the Absorption of Light by Coloured Media, and on the Colours exhibited 

 by certain Flumes, Ac. Sjc* By J. F. W. Herschel, Esq. Sec. R.S. 

 Lond. and F.R.S. Edin. 



1 h e composition of the solar rays has exercised the sagacity of philoso- 

 phers since the discovery of the different refrangibility of the rays of light 

 by Newton ; and though unquestionably it is to that great man that we 

 owe the first and prominent fact of the nonhomogeneity of white light, 

 yet much has been added to his discoveries by later research, and proper- 



• These two papers are printed in the Edinburgh Transactions, vol. is. p. 433 

 and 445. It will give us, as well as our readers, great satisfaction to hear frequent- 

 ly from the able correspondent to whom we are indebted for this analysis. — Ed. 



G 



