oils of
manganin constant for at least a year (in 1892 the tests had only been
made for this time) within a few thousands per cent. Manganin can be
obtained in sheets, and from this material standards of 10-2, 10-3,
and 10-4 ohms are made by soldering strips between stout copper bars,
and these are adjusted by gradually increasing their resistance by
boring small holes through them. The solder employed is said to be
"silver."

Mr. Griffiths (Phil. Trans. vol. clxxxiv. [1893], A, p. 390) has
had some experience with manganin carrying comparatively heavy
currents, under which circumstances its resistance when immersed in
water was found to rise in spite of the varnish which coated it.
Other experiments in which the manganin wire was immersed in paraffin
oil did not exhibit this effect, though stronger currents were passed.

On the whole, manganin appears to be the best material for coil boxes
and "secondary" resistance standards. Whether it is fit to rank with
the platinum alloys as regards permanency must be treated as an open
question.

Sec. 122. Other Alloys.

The following tables, taken from the work of Feussner and St.
Lindeck, Zeitschrift fuer Instrumenten Kunde, 1889, vol. ix. p.
233, together with the following notes, will suffice.

Sec. 123. Nickelin.

This is only German silver with a little less zinc, a little more
nickel, and traces of cobalt and manganese. It behaves like German
silver, but is an improvement on the latter in that all the faults of
German silver appear upon a reduced scale in nickelin.

Sec. 124. Patent Nickel.

Practically a copper nickel alloy, used to some extent by Siemens
and Halske. It stands pretty well in the same relation to nickelin as
the latter does to German silver. After annealing as for manganin it
can be made into serviceable standards which do not change more than a
few thousandths per cent. I have not come across a statement of its
thermo-voltage against copper.

Sec. 125. Constantin.

Another nickel copper alloy containing 50 per cent of each
constituent. It appears to be a serviceable substance, having a
temperature coefficient of 0.003 per cent per degree only, but an
exceedingly high thermo-voltage, viz. 40 micro-volts per degree
against copper.

1 2 3 4 5 6 7 8
German Nickelin made Rheo- Patent Nickel Manga- Nickel
Silver by Obermaier tane