[Footnote: Paper read before the Society of Telegraph Engineers, 14th
February, 1884.]


In consequence of the rapid development of that part of electrical
science which may be termed "heavy electrical engineering," reliable
measuring instruments specially suitable for the large currents
employed in lighting and transmission of energy have become an absolute
necessity. As usual, demand has stimulated supply, and many ingenious
and useful instruments have been invented, the manufacture of which
forms at the present day an important industry. Mr. Shoolbred, in a
paper which he recently read before this Society, gave a full and
interesting account of the labors of our predecessors in this field.
To-day we add to the list then given a class of instruments invented by
us, examples of which are now before you on the table. We have preferred
to call them current and potential indicators in preference to meters,
considering that the latter term, or rather termination, ought to be
applied rather to integrating instruments, which the necessities of
electric lighting, we believe, will soon bring into extensive use. The
principal aim in the design of these indicators has been to obtain
instruments which will not alter their calibration in consequence of
external disturbing forces. If this object can be attained, then it will
be possible to divide the scale of each instrument directly into amperes
or volts, as the cause may be, and thus avoid the use of a coefficient
of calibration by which the deflection has to be multiplied. This is an
important consideration when it is remembered that in many cases
these instruments have to be used by unskilled workmen, to whom a
multiplication involving the use of demical fractions is a tedious and
in some cases even an impossible task.