1867.] Conversion of Dynamical into Electrical Force. 367 



Fall of temperature at Madras, by nights : — 

 1. I 



2. 



Entirely clear sky (1-000). 

 25 nights, 

 o 



4-5 



7- 1 



8- 5 

 7-7 



7- 6 



11- 2 



9- 5 

 9-5 

 9-1 

 6-9 

 9-6 

 9-6 



12- 2 



8- 1 



9- 4 

 6-6 

 8-2 

 4-9 



6- 5 

 8-7 



8- 2 



7- 5 

 10-6 



9- 4 

 6-5 



25 ) 207-6 

 8-3 



Partially clouded sky (-915). 

 22 nights. 



Percentage of 

 Q clear sky. 



4- 8 -900 

 6-2 



5- 9 

 8-4 



4- 6 



5- 

 7-5 



7- 6 

 5-3 

 5-4 

 5-8 



8- 5 



99 



6-0 



•910 



3-6 



•920 



7-2 





7-6 





5-0 





6-7 





5-7 



•930 



4-2 





6-4 





4-9 





6-3 





) 132-6 



•915 Mean. 



At Fort Franklin, Sir John Richardson found that the maximum of solar 

 radiation was obtained in the spring and at noon. Mr. Forbes accounted 

 for this by the fact that the sun's rays were reflected from the snow, and 

 thus the bulb of the thermometers received reflected as well as direct rays 

 of sunshine. 



II. "On the Conversion of Dynamical into Electrical Force with- 

 out the aid of Permanent Magnetism.^^ Ey C. W. Siemens, 

 F.R.S. Received February 4, 1867. 



Since the great discovery of magnetic electricity by Faraday in 1830, 

 electricians have had recourse to mechanical force for the production of 

 their most powerful effects ; but the power of the magneto-electrical ma- 

 chine seems to depend in an equal me&sure upon the force expended on the 

 one hand, and upon permanent magnetism on the other. 



An experiment, however, has been lately suggested to me by my brother, 

 Dr. Werner Siemens of Berhn, which proves that permanent magnetism is 



