270 



Mr. Joule on the Calorific Effects 



o, 04< on account of the difference between the mean differences 

 0°'51 and 0°'36. The ground of this correction is the result 

 of a previous experiment, in which, by revolving the appara- 

 tus at 94° in an atmosphere of 60°, the water sustained a loss 

 of 7 0, 6, or about one quarter of the difference between the 

 temperature of the atmosphere and the mean temperature of 

 the water. 



With the same electro-magnet, but using a battery of only 

 four cells, arranged in a series of two double pairs, by which 

 I expected to obtain about half as much magnetism in the iron, 

 the following results were obtained : — 



No. 3. 



In the next experiments a battery of ten cells in a series of 

 five double pairs was used for the purpose of exciting the large 

 stationary electro-magnet. But, dismissing the galvanometer 

 and the other extra parts of the circuit, I connected the ter- 

 minal wires of the electro -magnet together, so as to obtain the 

 whole effect of the magneto-electricity. The resistance of the 

 coil of the revolving electro-magnet being to that of the whole 

 circuit employed in the experiments No. 2 as 1 : 1*13, and 

 0*902 of current being obtained in those experiments, I ex- 



