Miscellanies. 36 1 



occasion ; — this solemn warning made a deep, and it is hoped, a last- 

 ing impression on those who witnessed it, of the uncertain tenure by 

 which we hold our lives." Copied from the Ceylon Chronicle in the 

 Literary Gazette of Jan, 1839, — ih. 



33. Rose 3Iica Lcpidolite. — This mica has the form of very small rose- 

 colored plates. It is found disseminated in a kaolin, which is employed 

 in the porcelain manufactures of Vienna. It is separated by washing 

 from the kaolin. Tlie mean of four analyses gave 



Silica 



Alumina 



Potash 



Lithia 



Fluorine 



52 40 



26-80 

 914 



4-85 

 440 



Deutoxide of manganese . . 1.50 — ^9909 



Yellow Mica. 



Sili 



Alumina 



Peroxide of iron 

 Potash 



4 



Lithia 



Fluorine 



49-78 

 19.88 

 1 3 22 



879 



415 



4 24—1 00 



Annales de Chimic et de Phys., pp. 69-72.— ZoK<f. 4* Edin. Phil 3Iag. 



34. Notice of a cheap and simple method of preparing paper for 

 Photographic Drawing, in which the use of any salt of silver is 

 dispensed with; by Mungo Ponton, Esq., F. R. S. E., Foreign 

 Secretary Society of Arts for Scotland. Commumcated by the So- 

 ciety of Arts.* — While attempting to prepare paper with the chro- 

 mate of silver, for Avhich purpose I used first the chromate of potash, 

 and then the bichromate of that alkali; I discovered that when paper 

 was immersed in the bichromate of potash alone, it was powerfully 

 and rapidly acted on by the sun's rays. It accordingly occurred to 

 me, to try paper so prepared to obtain drawings, though I did not at 

 first see how they were to be fixed- The result exceeded my expec- 

 tations. When an object is laid in the usual way on this paper, the 

 portion exposed to the light speedily becomes tawny, passing more 

 or less into a deep orange, according to the strength of the solution, 

 and the intensity of the light. The portion covered by the object 

 retains the original bright yellow tint, which it had before exposure, 

 and the object is thus represented yellow upon an orange ground, 



* Read before the Society of Arts for Scotland 29th May, 1839. 

 Vol. xxxvii, No. 2.— July-October, 1839. 46 



