192 ACCOUNTS, ETC., OF THE BRITISH MUSEUM. 



All the thin-slices of rocks prepared during the year and 

 those belonging to the Phillips Collection have been micro- 

 scopically examined, and have been entered in the slip- 

 catalogue. 



III. — Preparation. 



Two hundred and thirty-one thin-slices of rocks have been 

 prepared- 

 ly. — Investigation. 



The crystallographic and chemical investigation of the 

 green fluo-arsenate from the manganese-ore deposits of India 

 has been completed, with the result that its identity with the 

 rare mineral tilasite occurring at Langban, Sweden, has been 

 established. Fermorite, a new arseno-phosphate of lime and 

 strontia, from the same deposits has also been examined, and 

 its optical characters and chemical composition have been for 

 the first time determined. 



The rare mineral schwartzembergite has been optically 

 and chemically investigated, and has been shown to be a 

 complex iodate and chloride of lead. 



Crystallized products from tin-furnaces have been examined' 

 crystallographically and analysed. 



Various sets of carat-weights have been compared, and an 

 inquiry has been made into the history of the larger diamonds 

 from South Africa, in order to ascertain the true weight of the 

 " Cullinan " and other large diamonds. For this purpose also, 

 new models of famous diamonds have been acquired and their 

 volumes have been determined. 



Crystals of the rare minerals phenakite and bertrandite 

 from Cornish localities have been measured and determined. 



Egyptian scarabs in the Collection at Bloomsbury, and 

 stone implements collected by Dr. C. G. Seligmann in the 

 Sudan and by Dr. M. A. Stein in Central Asia, have been 

 examined, and the materials of which they consist have been 

 determined. 



Crystals of whewellite, presenting a new habit, from Burgk, 

 Saxony, have been measured. 



The "light-figures" displayed by crystals of phacolite from. 

 Co. Antrim have been studied. 



In the chemical laboratory, quantitative analyses have been 

 made of tilasite, fermorite, schwartzembergite and crystallized 

 products from tin-furnaces, and many doubtful minerals have 

 been qualitatively analysed. 



V. — Donations of Duplicates. 



Duplicate specimens of mineraJs have been given to the 

 Kelvingrove Museum, Glasgow, and to Mr. J. S. Neil, of; 

 Wolverhampton. 



