Bose . — On Diurnal Variation of 
currents have to be kept up per hour. This necessitates the employment 
of an electric accumulator having a very large capacity. 
In the Oscillating Recorder the recording plate itself moves to and fro, 
making intermittent contact with the writer, about once in a minute. In 
Fig. 2 is given an illustration of the apparatus, reduced to one-fourth the 
actual size. The recording smoked glass plate is allowed to fall at a definite 
rate by the unwinding of the clock wheel W. The same clockwork, acting 
on an arrangement of alarum, previously described, causes, by means of the 
plunging rod R, periodic closures of the exciting circuit for a definite duration. 
M is an electromagnetic ar- 
rangement by which the holder 
of the smoked glass plate is 
made to oscillate to and fro, 
causing periodic contact with 
the writer. 
The Oscillator is dia- 
grammatically shown in Fig. 3. 
M, m' are the two electromag- 
netic coils, the free ends of 
the horseshoe being pointed. 
Facing them are the conical 
holes of the soft iron armature 
A. This armature carries 
two rods which slide through 
hollow tubes. The distal 
ends of the rods support the 
holder H, carrying the smoked 
glass plate. Under normal 
Fig. 3. The Oscillator. Electromagnet m, m', conditions, the plate - holder 
periodically magnetized by completion of electric current . • ui 
by clockwork c. Periodic attraction of soft iron arma- is held by suitable springs, 
ture A moves attached glass plate to left, making thereby somew h at to the right of, and 
electric contact with writer. . 
free from contact with, the 
writer. A clockwork c carries a rotating arm, which makes periodic 
contact with a pool of mercury contained in the vessel V, once in a minute. 
On the completion of the electromagnetic circuit, the armature A is 
attracted, the recording glass plate being thereby moved to the left, 
making contact with the writer. The successive dots in the record thus 
take place at intervals of a minute. Only a moderate amount of electric 
current is thus consumed in maintaining the oscillation of the plate. 
A 4-volt storage cell of 20 amperes capacity is quite sufficient to work 
the apparatus for several days. 
The responsive fall of the leaf of Mimosa is completed in the course of 
about two seconds. The leaf remains in the fallen or ‘ contracted ’ position 
