1823.] Acids in Mineral Substances. 387 



burned ; the salt volatilizing before ignition, most, or all, the 

 other nitrates deflagrate. 



If metallic copper is put into the solution of a nitrate, sulphu- 

 ric acid added, and heat applied, the copper dissolves with effer- 

 vescence. 



10. Carbonic Acid. — It is to be discovered in the mineral 

 itself. The application of heat is, in some cases, required to 

 render the effervescence sensible. It has been sometimes over- 

 looked in bodies from want of attention to this circumstance. 



11. Silica. — A simple and sufficient test of it is the formation 

 of a jelly, when its combination with soda is put into an acid. 



It has evidently not been intended to enumerate all the means 

 by which the presence of each acid in the soda bead could be 

 perceived or established. Little has been said beyond what 

 appeared required and sufficient. 



Mention has been made above of small plates of clay. 



They are formed by extending a white refractory clay by 

 blows with the hammer, between the fold of a piece of paper, 

 like gold between skins. The clay and paper, and then cut 

 together with scissars into pieces about 4-10ths of an inch long, 

 and 2^-1 Oths of an inch wide, and hardened in the fire in a 

 tobacco-pipe. 



They are very useful additions to the blowpipe apparatus. 

 They admit the use of a new test, oxide of lead. They show to 

 great advantage the colours of matters melted with borax, &c. 

 Quantities of matter too minute to be tried on the coal, or on the 

 platina foil, or wire, may be examined on them alone, or with 

 fluxes. Copper may be instantly found in gold or silver by fusing 

 the slightest scrapings of them with a little lead, &c. &c. 

 - Cut into very small, very acute triangles, clay affords a sub- 

 stitute for Saussure's sappare. 



Article XIV. 

 Analyses of Books. 



Narrative of a Journey to the Shores of the Polar Sea, in the 

 Years 1819, 1820, 1821, and 1822, By John Franklin, Capt. 

 RN. FRS. and Commander of the Expedition. With an 

 Appendix on various Subjects relating to Science and Natural 

 History. Illustrated by numerous Plates and Maps. Pub- 

 lished by Authority of the Right Honourable the Earl Bathurst. 



The late period of the month at which this most interesting 

 work has been submitted to our attention, in conjunction with 



2c2 



