676 



ACCOUNT OF THE 



abeund in carbonate ef lime. Th« Count dc Bournon lefers, 

 for a complete confirmation of his mineralogical opinions, 

 to Mr. Chenevix's chemical analjsis of all the substances 

 that he has examined, which is to form a continuation of 

 this elaborate essay. 



Some observations of the place of the planet Ceres, by 

 Professor Bode, of Berlin, were also communicated on 

 the 8th by Dr. Herschcl; and the Society adjourned to the 

 aoth. 



" Jit a Meeting of the Managers of the Royal Institution 

 of Great Britain, held at the Hojise of the Institution, on 

 the ith Day of April, 1 802. ^ 



" Restlved, That the Resolution of the Managers of the 

 Royal Institution, of the 31st of March, 1800, Article 4," 

 already inserted in the Journals, "be communicated to the 

 Royal Society; and that tlie Royal Society be requested 

 to direct their Secretaries to communicate, from time to 

 time, to the Editor of the Journals of the Royal Institu- 

 tion, such information respecting the papers read at the 

 meetings of the Society, as it may be thought proper to 

 allow to be published in those Journals." 



" At a Meeting of the Council of the Royal Society , on 

 the 15th of April, 1802. 



" Resolved, That the Council agree to the request of 

 the Royal Institution, as expressed in the above minute of 

 the 5th of April, and that they thankfully accept the offer 

 made them in the minute of the 3ist of March." 



In consequence of this resolution, the editors of the 

 Journals of the Royal Institution have the privilege of in- 

 specting all the papers communicated to the Royal Society, 

 and of extracting from them such notices as they may think 

 interesting to the public, without being sufficient to super- 

 sede the necessity of consulting the original memoirs, when 

 printed in the Philosophical Transactions. 



The Count dc Bournon's paper, on corundum, was con- 

 cluded on the 1 3th of May. After having considered the 

 matrix of imperfect corundum from the peninsula of India, 

 with the feltspar, the fibrolitc, the thallite, or epidote of 

 Hauy, the hornblende, the quartz, the talc and mica, 

 the garnets, the zircon, and the black oxid of iron, that this 

 matrix usually contains, some of them substances now first 

 named, the author proceeds to the matrix of imperfect co- 

 nmdum from China, and from the kingdom of Ava, 

 which is a granite rock, composed of feltspar, fibrolitc, 

 mica, and black oxid of iron, without the peculiar substance, 

 which is the basis of the matrix of the imperfect corundum 

 from the Carnatic ; sometimes a little chlorite and thallite 

 occiu in this piatriz. Next, the matrix of perfect corundiun 



from Ceylon is investigated, but it is principally frtjra con- 

 jecture that the author determines the spinelle ruby to be 

 one of the substances accompanying it, since it is found in 

 the sands, together with the corundum. The crystals of 

 the spinelle are described as either complete tetraedons, or 

 rhomboids, with plane angles of eo", or dodecacdrons, or 

 lastly tetraedral prisms terminated by pyramids : its colour 

 is often yellowish or bluish. Its matrix is sometimes a cal- 

 carious stone, and sometimes a kind of adularia. Another 

 substance frequently found in these sands is the tourmalin. 

 Its primitive crystal is a very obtuse rhomboid ; the solid 

 angle being 139° ; the second form is a prism, either hex- 

 aedral, enneaedral, or dodecacdral, abruptly terminated; and 

 there are some other varieties : the colour differs very consi- 

 derably in different specimens ; it is sometimes yellowish, 

 bright green, or purplish red ; and sometimes the crystals are 

 colourless. A specimen of remarkable magnitude and beauty 

 is mentioned, which was presented to Mr. Symes by the 

 sovereign of Ava, and placed by him in Mr. GreviUe's 

 collection. The Ccylonite of Lametherie, or the plconast 

 of Haiiy , is also found in the sands of Ceylon ; it is usually 

 of a brownish green, and it greatly resembles the spinelle, 

 but is somewhat softer. Small crystals of zircon, with 

 scattered fragments ofsome other stones, help also to com- 

 pose this sand, as it is sent to Europe. Of all these sub- 

 stances, the spinelle is the most abundant. 



It apiiears to be doubtful, whether or no corundum is 

 found in any part of the world, except the East Indies ; 

 yet the Count de Bournon has reasons for thinking that 

 it has been discovered in some of tlie mountains of France. 

 But the specimens from Germany, and from Tiree, appetr 

 to have been of other descriptions. Whether or no it has 

 been found in the neighbourhood of Philadelphia, is a dis- 

 puted point. Mr. Haiiy considers the specimens from the 

 neighbourhood of Montbrison as a harder kind of feltspar : 

 but the Count de Bournon is persuaded that they are co- ' 

 rundums, nearly resembling the sapphire, but combined in 

 some degree with feltspar. The emeralds found in the same 

 place are more strongly characterized. 



On the 6th of May, Dr. Herschel's observations on the 

 two lately discovered celestial bodies were read. 



Dr. Herschel begins with stating the result of his at- 

 tempts to measure the diameter of the stars discovered by 

 Piazzi and Olbers. He employed the lucid dioc microme- 

 ter, which consists of an illuminated circle, viewed with 

 one eye, while the other compares with it the magnified 

 image formed by the telescope ; and he concludes, that 

 the apparent diameter of Ceres was .22", and of Pallas .17" 

 or. 13", at the distance of nearly 1.634, and 1.187 from 

 the earth respectively, whence the apparent diameters at 



