It will be easily understood that as the bobbin hangs freely in the
center of a very strong magnetic field (formed by the four poles of the
two permanent magnets), the slightest current sent through the bobbin
will cause the bobbin to be attracted from one direction, while it will
be repelled from the other, according to the polarity of the current
transmitted.
As the relay has a very low resistance, it is evident that it will
become an acceptable auxiliary in our central office, particularly when
used as a "calling off" signal, as by its use the ground deviation, so
objectionable and yet so universally used for "calling off" purposes,
can be entirely avoided, and the relay left directly in the circuit, as
is being done here in Paris. R. G. BROWN.
Paris, September 12, 1882.
* * * * *
THE PLATINUM WATER PYROMETER.
By J. C. HOADLEY.
The following description of the apparatus used for the determination
of high temperatures, up nearly to the melting point of platinum, is
offered in answer to several inquiries on the subject:
The object to be attained is a convenient and reasonably accurate
application of the method of mixtures to the determination of
temperatures above the range of mercurial thermometers, say 500 deg.
Pages:
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112