ng a trace of tungsten.

The resistivity of non-metallic conductors is in all cases higher than
that of any pure metal. The resistivity of carbon, for instance, in the
forms of charcoal or carbonized organic material and graphite, varies
from 600 to 6000 microhms per cubic centimetre, as shown in Table VI.:--

TABLE VI.--_Electric Volume-Resistivity in Microhms per
Centimetre-cube of Various Forms of Carbon at 15 deg. C._

+-----------------------------------------+---------------+
| Substance. | Resistivity. |
+-----------------------------------------+---------------+
| Arc lamp carbon rod | 8000 |
| Jablochkoff candle carbon | 4000 |
| Carre carbon | 3400 |
| Carbonized bamboo | 6000 |
| Carbonized parchmentized thread | 4000 to 5000 |
| Ordinary carbon filament from glow-lamp | |
| "treated" or flashed | 2400 to 2500 |
| Deposited or secondary carbon | 600 to 900 |
| Graphite | 400 to 500 |
+-----------------------------------------+---------------+

The resistivity of liquids is, generally speaking, much higher than that
of any metals, metallic alloys or non-metallic conductors. Thus fused
lead chloride, one of the best conducting liquids, has a resistivity in
its fused condition of 0.376 ohm per centimetre-cube, or 376,000
microhms per centimetre-cube, whereas that of metallic alloys only in
few cases exceeds 100 microhms per centimetre-cube. The resistivity of
solutions of metallic salts also varies very largely with the proportion
of the diluent or solvent, and in some instances, as in the aqueous
solutions of mineral acids; there is a maximum conductivity
corresponding to a certain dilution. The resistivity of many liquids,
such as alcohol, ether, benzene and pure water, is so high, in other
words, their conductivity is so small, that they are practically
insulators, and the resistivity can only be appropriately expressed in
megohms per centimetre-cube.

In Table VII. are given the names of a few of these badly-conducting
liquids, with the values of their volume-resistivity in megohms per
centimetre-cube:--

TABLE VII.--_Electric Volume-Resistivity of Various Badly-Conducting
Liquids in Megohms per Centimetre-cube._

+--------------