1$17.] Linneean Society. 153 
capable of exploding the mixture, it was yet capable of heating the 
platinum to redness. On making exploding mixtures of oxygen 
with hydrogen, and other inflammable gases, and plunging a hot 
platinum wire into them, he found that it became red hot, and 
continued so till the mixture had lost its power of exploding. 
Vapour of ether, alcohol, or naphtha, mixed with air, had the same 
property. He describes an experiment which every person can 
make, and which serves admirably to illustrate the fact. Let a drop 
of ether fall into a glass vessel, heat a platinum wire by means of a 
hot poker, and plunge it into the vessel. It will immediately become 
red-hot in some part, and continue so till the ether is consumed. 
During this silent combustion of the vapour of ether there is a 
phosphorescent light connected with some curious chemical changes 
which take place in the ether, and which he is at present engaged 
in investigating. 
Platinum answers best for these experiments, on account of its 
small capacity for heat, and itssmall radiating power. The author 
tried silver, copper, and iron, but did not succeed with any of them. 
But as the wires of these metals were not very small, he does not 
consider the point as decided by the experiments which he has 
hitherto made. He terminated his communication with a practical 
application to coal-mines. If a wire of platinum be suspended 
over the flame of a safety lamp properly coiled up, and if the lamp 
be taken into an exploding mixture, it will be extinguished, but 
the platinum wire will become red hot, and will continue to give 
out light till the mixture loses its exploding qualities. By this light 
the miner may direct his way out of the exploding mixture. 
I consider this as one of the most beautiful discoveries which Sir 
H. Davy has made. The numerous practical applications of it to 
gaseous experiments must be obvious to chemists in general. 
At the same meeting a paper, by Dr. Brewster, on Light, was 
read. This paper consisting of a great number of detached facts, 
it is difficult to give any account of it. He showed how the metals 
by their polarization of light form the supplementary colours. He 
stated also that common salt and fluor spar, when in pieces large 
enough, act upon light in the same way as doubly-refracting bodies. 
LINNEAN SOCIETY. 
On Tuesday, Dec. 3, a description was read of a fossil belemnite 
in flint, by Dr. Arnold. The specimen was remarkable, because 
it exhibited a very distinct jointed syphunculus passing through the 
fossil, Very little is known respecting the nature of the animal 
that inhabited this fossil. Dr. Arnold conceives that it was capable 
of rising or sinking in water at pleasure, and that its structure was 
somewhat similar to that of the nautilus or cornu ammonis, 
At the same meeting several specimens of an unknown fossil in 
flint, sent by Dr. Arnold, were exhibited. ‘They consist of small 
flat spherical bodies, having a depression in the centre, in which is 
6 
