The stone was dried in the sun for three weeks in the summer (United
States), and the wood is described as having been well seasoned:-

CURRENT WITH THE GRAIN

Lowest Resistance Highest Resistance Lowest Specific Highest Specific
between two Cups between two Cups Resistance in Resistance in
in Megohms. in Megohms. Megohms. Megohms.

Ash.

550 920 380 700

Cherry

1100 4000 2800 6000

Mahogany

430 730 310 610

Oak

220 420 1050 2200

Pine.

330 630 360 1470

Hard pine.

10 48 17 1050

Black walnut

1100 3000 320 2100

Red fibre

2 4 3 60

Slate

184 280

Soapstone.

330 500

White marble

2000 8800

Sec. 115. As to working the materials very little need be said.

Fibre is worked like wood, but has the disadvantage of rapidly taking
the edge off the tools. In turning it, therefore, brass-turning
tools, though leaving not quite such a perfect finish as wood-turning
tools, last much longer, and really do well enough. Fibre will not
bear heating much above 100 deg.C--at all events in paraffin. At 140 deg.
C. it becomes perfectly brittle. Its chief merit lies in its great
strength. So far as insulation is concerned, Mr. Peirce's experiments
show that it is far below most kinds of wood.

Slate. This is a vastly more useful substance than it is generally
credited with being. It is very easily worked at a slow speed, either
on the shaping machine or on the lathe, with tools adjusted for
cutting brass, and it keeps its figure, which is more than can be said
for most materials. It forms a splendid base for instruments,
especially when ground with a little emery by iron or glass grinders,
fined with its own dust, and French polished in the ordinary way.
Spools for coils of considerable radial dimension may be most
conveniently made of slate instead of wood or brass, both because it
keeps its shape, and because it insulates suff