The interrupting system is symmetrical with the first. It consists of
the style, s, of the spiral spring, f, of the screw, v, and of the
plate that this carries at its extremity. The terminal, B, which carries
the spring, f, and the rod which carries the screw being insulated
from each other, it is only necessary to cause to terminate therein the
extremities of a circuit comprising one pile, in order to produce in the
circuit a number of interruptions equal to that of the tuning fork's
vibrations. Provided the lengths of the springs, f and _f'_, are
proper, such vibrations will not be altered.
Moreover, the instrument is so arranged as to produce vibrations whose
_duration can be varied at pleasure and kept constant_ during the whole
time the experiments last. This is done by modifying the _amplitude_ of
the vibrations; for the greater the amplitude, the longer likewise the
duration of the contact of the style, s, on the corresponding plate,
and the shorter the duration of the interruption. In order to modify the
amplitude, the action of the electro-magnet on the branches of the
apparatus is made to vary. To effect this, the electro-magnet is made
movable perpendicularly by the aid of a screw, V, between two slides, so
that the core, N, may be moved with respect to the median line of the
branches, and even be raised above them. Its action diminishes,
necessarily, while it is being raised, and the amplitude of the
vibrations likewise diminishes gradually and continuously.
Pages:
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128