154 Scientific Intelligence. [Feb. 



the numbers stated by Mr. L., the progress of the differential ther- 

 mometer from and towards the mirror, indicates the very ratio that 

 the prismatic spectrum displays with regard to intensity of light. 

 What then must be our conclusion, but that the reflector in this 

 case performs an office similar to that of the prism ? * 



Now, Sir, may we not take advantage of this instrument to ob- 

 tain a better knowledge of those rays termed deoxidating? la 

 ■ conformity to my theory another focus remains to be discovered, 

 where muriate of silver would be found to blacken most readily j 

 for I contend, that those rays are mere modifications of heat, or, 

 to speak more fully, that they are rays of latent caloric, or the 

 true phlogiston ; while those which affect the thermometer are 

 obvious or sensible caloric. With the greatest respect, 



I am, Sir, Yours, Sec. 



David Huston. 



VI. Position of Port Jackson, New Holland. 



From the observations of Captain Flinders, it appears that 

 Cattle Point, on the east side of Sidney Cove, is in latitude 33* 

 51' 45-6", south 3 longitude, 151° 11' 49'', east.— Flinder's 

 Voyage f I. 237. 



VII. Chinese Paste. 



The method of making paste in China is much more economical 

 dian the mode followed in this country. Were it universally adopted 

 by trunk-makers, book-binders, and others, who use great quan- 

 tities of paste, it would produce a very material saving of flour, 

 which in years of scarcity might be of the greatest consequence. 

 The following formula used in China was lately communicated to 

 the Right Hon. Sir Joseph Banks, Bart., by a gentleman at present 

 in Canton. — Mix together bullock's blood and quick-lime, in the 

 proportion of one pound of the latter to lOlbs. of the former. It 

 becomes a stiff jelly, in which state it is sold to the consumers, who 

 beat it down with an addition of water into a state sufficiently fluid 

 for use. At Canton it will keep five or six days in the hot weather 

 and ten or twenty days in the cold. In Britain it would probably 

 keep longer. 



VIII. Chinese Method of casting Sheet Lead. 



The Chinese method of casting sheet lead is very simple. Two 

 large flat tiles are used for the purpose, covered on the inside with 

 thick paper. The workman opening them a little at top, pours in 

 a small quanthy of melted lead, and pressing the tiles together 

 with his foot, forms the sheet. A kind of resin called dummer is 

 used to prevent the oxydizement of the metal. The tea canisters 



♦ As soand (a) is reflected as >rell as light and heat by a concave mirror, I 

 have little doubt but that their analogy ivill be one day perfectly demonstrated. 



(a) Query. Is the focui of sound at the same distance from the reflector as 

 the focus of light? 



