TRANSACTIONS OP THE SECTIONS. 77 



a knife, and exposed to the air. This phosphoric light, like that of potassium, lasts 

 for a few minutes only at the ordinary temperature of the atmosphere ; but at a tem- 

 perature of about +70° (Centigrade), the light emitted by sodium nearly equals that 

 given out by phosphorus itself. 



I have lately observed also that copper, native sulphuret of copper, and silver are 

 notably phosphorescent by heat. With copper the fact is most striking. In order to 

 observe the phenomenon, one or two grammes of copper should be melted before the 

 blowpipe in a cavity made in a piece of charcoal. As soon as the copper is thoroughly 

 melted (at the inner flame) it glows with a greenish yellow phosphoric light, similar 

 to that of the glow-worm. On cooling a little it rapidly loses this property, and at 

 the same time a molecular change is observed on the surface of the metal. Native 

 sulphuret of copper (Chalkosine) is likewise phosphorescent when melted before the 

 blowpipe. Silver becomes slightly phosphorescent only for an instant on cooling, 

 just before it leaves the liquid state. 



I have found also that the mineral Lepidolite is quite as phosphorescent by heat as 

 fluor-spar. But to see this phenomenon perfectly, it should be viewed through a 

 piece of glass coloured blue by oxide of cobalt. When seen in these circumstances, 

 the phosphoric light of Lepidolite is very fine ; and, when seen through the cobalt 

 glass, the phosphorescence of fluor-spar is far more brilliant than when observed with 

 the naked eye. 



This mode of experimentation is probably applicable to all substances that are 

 phosphorescent by heat. 



Composition of the Shell of Cardium edule {Common Cockle). 

 By Dr. T. L. Phipson, of Paris. 



The specimens analysed were taken on the coast of Ostend (Belgium). The best 

 of five analyses gives for their composition : — 



Water 1*10 



Organic matter 4*44 



Carbonate of lime 92"93 



Phosphate of lime 0*12 



Sulphate of lime 0*34 



Magnesia 0*13 



Peroxide of iron 0'41 



Alkalies traces 



Silica 0-53 



100-00 



Composition of a recently -formed Rock on the Coast of Flanders. 

 By Dr. T. L. Phipson, of Paris. 



This rock, which I described some time ago in the ' Comptes Rendus ' of the Aca- 

 demy of Sciences of Paris (23rd March, 1857), and which has likewise been mentioned 

 in the pages of ' The Geologist,' vol. i. 1858, London, as being deposited daily from 

 the sea, at about a league from the coast of Ostend, is of a light grey colour. I have 

 lately submitted it to analysis. It presents the following composition : — 



Water and organic matter 2*5 



Sand 57-4 \ „„ . 



Grey clay 6*0 J 



Carbonate of lime 30*8 



Magnesia (small quantity) "I 



Phosphate of lime (small quantity) > 1*7 



Alumina (small quantity) J 



Peroxide of iron ]*6 



100-0 

 Certain samples of this rock have a peculiar stratified appearance. It contains 



