1818.] Scientific Intelligence. . 143 



Article XVII. 



SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Effect of Camphor on heated platina Wire. 



The method of keeping a platina wire incandescent by means 

 of the vapour of alcohol has been fully described in a former 

 number of this journal. Sir H. Davy has discovered that the 

 vapour of camphor will produce a similar effect. For this pur- 

 pose lay a piece of camphor, or a few fragments on any conve- 

 nient support, and place upon it a coil of platina wire made red 

 hot ; the wire will immediately begin to glow, and will continue 

 in that state as long as any of the camphor remains. 



II. Silver from Luna Cornea. 



The following method of obtaining metallic silver from luna 

 cornea has been discovered by M. Arfvedson : 



Put some grains of zinc into a conical glass, and cover them 

 with luna cornea ; then pour in carefully some diluted sulphuric 

 acid. The hydrogen gas thus liberated will soon reduce the 

 silver to the metallic state. 



III. Geological Situation of the Gems of Ceylon. 



From a letter of Dr. J. Davy's, inserted in the last number of 

 the Royal Institution Journal, it appears that gems abound in 

 the district of Matura, situated in the south of the island of 

 Ceylon. They are procured by the natives from alluvial soil ; 

 but the native repository of the sapphire, the ruby, the cat's eye, 

 the different varieties of zircon, and cinnamon stone, has been 

 ascertained by Dr. D. to be gneiss. 



IV. Geological Description of Ada??i's Peak in the Island of 

 Ceylon. By Dr. Davy.* 



" Geologically considered, the mountain may be said to be 

 composed of gneiss. The rock on the top, on which is the 

 impression of the foot, is gneiss of a very fine grain. It abounds 

 in quartz. It is hard and compact, of a grey colour, and only 

 in mass exhibits a flaky structure. A little below, felspar pre- 

 dominates, and the rock is rich in garnets. Here it is in a soft 

 state ; and towards the surface rapidly decomposing. Still 

 lower, hornblende prevails, and in so large a proportion that 

 particular masses may be called hornblende rock. Near the 

 bottom, felspar again predominates, and the rock contains much 

 molybdena disseminated through it. Besides, in different 

 places the rock exhibits other peculiarities ; here abounding in, 



* Extracted from an account of Adam'i Peak in the Journ. of Science and the 

 Arti, v. 25. 



