Intelligence and Miscellaneous Articles. 73 



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At 0. B.B. 110. Temp, of shade 73. T Sky cloudless, but with a good 

 (Exposed to the sun and sky.) < deal of white vapour, more 



especially about the sun. 

 4. B. B. 90. Temp, of shade 73. 



(Shaded from sun by a 2-in. screen.) 

 30. B. B. 104. Temp, of shade 73. Light air. 

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35. B. B. 94. Temp, of shade 73. Light air. 



(Shaded from sun by a ^-in. screen.) 



1 0. B. B. 108. Temp, of shade 74. Quite calm. 



(Exposed to sun and sky.) 

 1 5. B. B. 109. Temp, of shade 74. Quite calm. 



(Exposed to sun through a 2-in. circular aperture in a 12-in. screen.) 

 1 15. B. B. 108. Temp, of shade 74. Quite calm. 



(Exposed to sun and sky.) 

 1 18. B. B. 106. Temp, of shade 74. Quite calm. 



(Exposed to sun through a 2-in. circular aperture in a 12-in. screen. 

 1 20. B. B. 106. Temp, of shade 74. Quite calm. 



(Exposed to sun but screened from sky.) 



XI. Intelligence and Miscellaneous Articles. 



ON THE LAWS OF INDUCTION. BY MM. JAMIN AND ROGER. 



n^HE experiments we are about to describe were arranged like those 

 -*- which are made on induction. A current interrupted at regular 

 intervals by a mercury contact-breaker traverses an inducing coil the 

 resistance of which is b ; in this is placed the induced coil, the resist- 

 ance of which is jG ; in the centre is a bundle of annealed iron wires. 

 The two ends of the inducing coil are connected with the two arma- 

 tures of a Fizeau's condenser ; lastly, both the induced and the in- 

 ducing coil may be lengthened by scales of varying resistance, which 

 we shall designate by 6 and t, and which may be increased from zero 

 to infinity. 



The peculiarity of our apparatus is that the coils, the soft iron, the 

 condensers, and the resistances and t are immersed in an insulating 

 liquid (oil of turpentine or benzole) in separate vessels hermetically 

 closed and terminated by divided thermometric tubes. By means of 

 a levelling tube with a stopcock the liquid in these tubes may always 

 be brought to a fixed height ; each apparatus constitutes therefore a 

 thermorheometer. As its electrical motion creates a quantity of heat 

 proportional to its vis viva, the liquid receives this heat, and the ex- 

 pansion measures it. We shall omit any details as to these experi- 

 ments, and restrict ourselves to giving a resume of the facts. 



Induced current. — The induced coil is connected with the scale 

 of resistance 6, which varies from zero to infinity. The quantities of 

 heat, C, C v produced in the unit of time in this resistance and in this 

 coil are measured. We may always write 



a, a 



cc being the total duration of the passages of the inducing current 



