110 Scientific Intelligence. 
then blowing. While the wind is from a given direction, the same 
crayon rests upon the cylinder, and leaves a trace, the length of which 
ow long it continued; and when the va h s, another 
It is seen that whilst the axis which carries these electro-magnets turns 
by means of a clock movement, each electro-magnet is magnetized as 
often as the wind causes the crayon to act which is in communication 
with the helix of this electo-magnet. But each time that this electro- 
magnet is set in action, the soft iron armature which turns around with 
it also in the 12 hours, and which is kept raised by an opposing spring, 
number marked by this counter. Finally, M. 
is able to indicate directly by his apparatus the monthly means for the 
rapidity of the wind. 
circular Electro-magnets.—I give in this place some brief ex- 
o the i 
ommunicates with the pile by the known methods ; in the second, itis 
directly connected with the poles of the battery, for it is fixed and the 
