458 Intelligence and Miscellaneous Articles. 
at tbese limits cos it is null, as also are the four terms of A. We 
have then, with a sufficiently near approximation, 
Y= 5m* sine*"' 'i' 2 c ° s '« rf " 
2 dt E 2 p ! tt /-, . 2p 
^a [ 1 + ^- cos e sin tt + 
u y 
In order to calculate approximately the value of the integral, we 
shall in the result neglect the terms of the second order in respect 
of the relation £., which is supposed very small. We have then 
TT 
T= — m -^sine^r ~ I cos 2 u( 1 — =£ cos e sin u ]du. 
2 dt K~ I J_jr \ E / 
2 
The value of this integral is ^ ; we have therefore finally 
TK dl . 7T0 3 7TO 
= _ ju sme-t-r -£. 
2 <A E 2 2Z 
Let us now suppose that the solenoid has the same radius as the 
sun, and that the distance E at which the induced mass m is placed 
is that which separates the earth from its luminary. We have 
then 
E=22095 . P ; |L =0-000020484. 
The fourth of the circumference of the earth is 100,000 hecto- 
metres ; the corresponding term for the sun is therefore 10,855,000 
hectometres. If we assume that the electric currents succeed each 
other upon the sun at a distance I, expressed by a fraction -th of 
a hectometre, we shall have 
and consequently 
fa g-i.. 222-35; 
-m^ir sinew. 222-35. 
2 dt 
To know whether this inductive force is efficacious at the distance 
at which the eai'th is placed, and without giving excessive values to 
di 
, we have only to compare it with an analogous force produced 
by a laboratory experiment and giving sensible effects. This I 
intend doing. 
For a system of spherical solenoids which should be concentric, 
similar to each other, and similarly placed, and of which all the 
currents experienced the same momentary variation of intensity, 
