366 



a little below the origin of the third nerve, fibres of which pass 

 directly through it ; but I am at present uncertain whether any of 

 them originate from its cells. It is much more distinct in some 

 animals than in Man. 



The corpora albicantia are ganglionic masses containing a multi- 

 tude of cells, which are mostly round, oval, pyriform, fusiform, 

 triangular, and quadrangular, and lie amongst the winding fibres of 

 the anterior pillars of the fornix. These cells vary considerably in 

 size, but are generally small ; the diameter of the largest of the 

 spherical kind being about the 2000th of an inch. The two bodies 

 are united across the middle line by a transverse commissure of fibres 

 containing cells which are fusiform in the same direction. 



Except when stated to the contrary, the above notes refer ex- 

 clusively to the structure of the human brain. 



XV. " On the Influence of Atmospheric Pressure upon some 

 of the Phenomena of Combustion." By Dr. EDWARD 

 FRANKLAND, F.R.S. Received June 20, 1861. 



(Abstract.) 



The author has concluded his experiments upon this subject ; and, 

 in addition to the details of the results which have already been 

 briefly mentioned in the 'Proceedings of the Royal Society'*, com- 

 municates the following : 



Although the rate of burning of candles and other similar com- 

 bustibles, whose flames depend upon the volatilization and ignition 

 of combustible matter in contact with atmospheric air, is not per- 

 ceptibly affected by the pressure of the supporting medium, yet this 

 is not true of all combustibles. The rate of burning of self-support- 

 ing combustibles, like the time-fuses of shells, depends essentially 

 upon the pressure of the medium in which they are deflagrated. 

 Attention was first called to this fact by Quartermaster Mitchellf , 

 who found that the fuses of shells burnt longer at elevated stations 

 than when ignited near the level of the sea. The results of the 



* Proceed. Royal Soc. vol. xi. p. 137. 

 t Ibid. vol. vii. p. 3 16. 



