TABLE III.-Experiments C, on Hard Quartz; pressure transverse to lamination.

TABLE IV. Experiments D, on Hard Quartz; pressure

parallel to lamination.

Pressure due to

TABLE V.-Experiments E, on Soft Slate; pressure

transverse to lamination.

NOTE. The cube E was 0.693 inch on the side, and the necessary reductions have been made in column 2 and subsequent ones.

TABLE VI.-Experiments F, on Soft Slate; pressure

Number of

experi

ment.

parallel to lamination.

Pressure due to the unit of surface

1 square inch.

Compression
readings of the

column
of 0.707 inch.

Compression readings due to the successive loads.

Total compressions produced by the loads in column of 0.707.

Total compressions reduced to

a column of unit height=1 inch.

TABLE VII.-Experiments G, on Soft Quartz; pressure

NOTE.-The cube F was 0.693 inch on the side, and the necessary reductions have been made in column 2 and subsequent ones.

transverse to lamination.

NOTE. The cube G was 0.694 inch on the side, and the necessary reductions have been made in column 2 and subsequent ones.

TABLE VIII.-Experiments H, on Soft Quartz; pressure

parallel to lamination.

Soft

Quartz.

NOTE. The cube H was 0.695 inch on the side, and the necessary reductions have been made in column 2 and the subsequent ones.

TABLE IX.-Slate Rock.-Results of compression compared.—Column of unit length=1 inch.

Quartz Rock.-Results of compression compared.-Column of unit

length=1 inch.

An examination of these Tables presents some remarkable and, so far as I am aware, now for the first time observed results.

As might have been expected, the quartz-rock is much less compressible generally than the slate-rock, with this exception, however, that the softest specimens of quartz-rock, and those alone, are much more compressible than the softest slate, when both compressed in the direction of or parallel to the lamination.

In this direction of compression, the hardest slate is more than double as compressible as the hardest quartz.

When compressed transverse to the lamina, however, the hard slate and hard quartz prove to have very nearly the same coefficient of compres sibility, which is very small for both; while the softest slate and the softest quartz, compressed in the same way (transverse to lamina), have also nearly the same coefficient of compressibility, but one about four times as great as for the hardest like rocks.

These facts point towards the circumstance of the original deposit and formation of these rocks as their efficient causes. Both rocks consist of