Si^ Dr. Schweiggev-Seiclel on the Blue Coloiiring-mattcr 



The several points I have enumerated place the theory oi" 

 the figure of the planets upon grounds entirely new. I con- 

 ceive that the views I have developed are important, both be- 

 cause they overcome a difficulty insuperable in any other way, 

 and because tliey will facilitate the progress of knowledge 

 by superseding much of the abstrusest and least satisfactory 

 writings on the celestial mechanics. Mj' only object in what 

 I have written is to assert and prove my claim to what I have 

 discovered, by my own labour, in spite of much unprecedented 

 opposition. I put myself in comparison with no one ; 1 will 

 enter into no altercation on the subject ; I merely claim what 

 I have the justest title to claim ; nor do I think it necessary at 

 present to explain particularly the reasons that have induced 

 me to write this letter. 



It may be proper to add that the subject of this letter has 

 no connection with another contestation, entirely mathemati- 

 cal, relating to the series for computing the attraction of sphe- 

 roids. I remain. Gentlemen, yours, &c. 



March 8, 1830. James Ivory. 



XXXV. On the Blue Colourhig-matter of Lapis Lazuli, and on 

 artificial Ultramariiie. ^j/Dr.FR.W. Schweigger-Seidel.* 



''I^HE mineral colour known by the name of Ultramarine, 

 •*■ esteemed for its beauty and durability, especially in oil- 

 painting, has long been an object of cliemical inquiry. The lapis 

 lazuli, from which the colour is obtained by careful washings, 

 is procured from Asia (partly through the East Indies, partly 

 by way of Orenburg), where it is found in Little Bucharia, 

 Thibet, several provinces of China, and Siberiaf. It seems to 

 have been known to the Romans under the name of Sapphire, 

 as appears from some passages of Pliny|. But the produc- 

 tion of ultramarine seems not to have been invented till the end 

 of the fifteenth century ; the name of Azurrum ultramarinum 

 (the origin of which is very evident) is said to have been first 

 used in the year 1502 by Camillus Leonarius§. It once 

 formed a considerable article of trade in Italy, where this co- 

 lour was probably first produced, and even now the greatest 

 quantity, and that of the best quality, comes from there. 



* From the Jahrbuch der Chemic, &c. N. R. Band xxii. p. 206. 



f This is different from the laziilite or cojjj^cr laziirc {krvnenivin ^ione), 

 which owing to the similarity of their colour used formerly to he mis- 

 taken for it ; hauyn seems to be more nearly related to lapis lazuli. 



X lli^t. Xat. lih. xxxvii. 38, 39. 



§ Lcuchs's Farhcn-tmd Fdrbekundc, ii. 198. 



Whether 



