68 Royal Institution of Great Britain. 



FRIDAY-EVENING PROCEEDINGS AT THE ROYAL INSTITUTION 

 OF GREAT BRITAIN. 



March 26. — Mr. Brooke on the principles of the doctrine of life 

 contingencies. Mr. Brooke developed the manner in which from 

 time to time the probabilities of life had been deduced by the Go- 

 vernment and by Life-assurance companies, explaining his statements 

 by reference to tables and to many curious and singular facts in the 

 philosophy of population. 



April 2. — Mr. Ainger on the theory of the radiation of heat. Mr. 

 Ainger's point was to explain a difficulty in M. Prevost's theory of the 

 radiation of heat, dependent upon the manner in which surrounding 

 objects frequently influenced the apparent quantity of radiation from 

 a given central heated body, as a thermometer, in complicated and 

 frequently unperceived ways. By taking into account the tempera- 

 ture of all these bodies, and the reflective as well as radiating power 

 of such as were important, he showed that the difficulty really had no 

 existence. He pointed out also by an experiment, that a given body 

 with a constant temperature and surface might appear either hot or 

 cold to the same thermometer according to the temperature of the 

 surfaces, the rays from which would be intercepted by the body and 

 prevented from impingeing on the thermometer. 



There were no meetings in Passion and Easter weeks. 



April 23. — Mr. Faraday on the flowing of sand under pressure. 

 This was an experimental account of the very curious experiments 

 made by M. Huber Burnand on the intermediate properties which 

 sand exhibited between those of solid and fluid bodies. Sand pre- 

 pared so as to be uniform and free from dust will flow in the air at 

 angles above 30 or 32 degrees, but not at smaller angles. Sand put 

 into a box or reservoir and allowed to flow out at an aperture, either 

 in the bottom or side, amounts to the same quantity passed, whatever 

 the head of sand may be, or whatever the pressure there exerted, be- 

 ing in this respect quite unlike fluid ; so that perhaps it may be made 

 to constitute a moving force probably more independent of deranging 

 causes than any other which can be devised. When a perpendicular 

 tube is filled with sand, very little of the weight is borne by the bot- 

 tom of the tube ; indeed only so much as would equal the weight of 

 a cone of sand standing on that bottom ; but nearly the whole is 

 supported by the sides. If a tube an inch in diameter be filled for 

 about six inches or more with sand, and laid horizontally, all attempts 

 to push the sand out of the tube by a stick of nearly the same dia- 

 meter will fail. These and many more curious facts, with their ge- 

 neral principles and applications, were explained and illustrated. 



April 30. — Dr. Clarke on the ascent and descent of Mont Blanc. 

 Dr. Clarke had on a former evening given an account of his ascent up 

 Mont Blanc ; he now concluded his account, and went at considerable 

 length into the geology and botany of the mountain. His obser- 

 vations were illustrated by numerous specimens of minerals and plants, 

 and also by drawings. 



May 7. — Mr. Faraday gave an account of the triangulation which 

 has been proceeding in Ireland for some years past, under the direc- 

 tion 



