Quarterly Scientific Intelligence [pp. 350-356]

Quarterly Scientific Intelligence.
of less than 0.1 inch of the manometer, but by the plan proposed the vacuum is perfect so far as it is indicated by the
manometer. Into the receiver of an ordinary air pump, which
is not required to exhaust further than to 0.3 or 0.5 of an inch,
but which must be capable of retaining a vacuum, two shallow
open vessels are placed, one above the other, as in the common
experiment of freezing water by the cold produced by its evaporation, the lower one containing concentrated sulphuric acid,
and the upper a concentrated solution of caustic potash. The
precise proportions of these liquids is not important, provided
that they are so adjusted that the acid is capable of completely
desiccating the potash solution without being much reduced in
strength, but at the same time that it does not expose so large
a surface as completely to dry the potash in less than five or
six hours. The pump is worked till the air in the receiver has
an elastic force of 0.3 or 0.4 of an inch, and the stop-cock
below the plate is then closed. A communication is now established between the tube for admitting air below the valves and
a gas-holder containing carbonic acid prepared with care to
exclude atmospheric air. After all the air has been removed
from the connecting tubes by alternately exhausting and admitting carbonic acid, the stop-cock below the plate is opened, and
the carbonic acid is allowed to pass into the receiver. The
exhaustion is again quickly performed to the extent of half
an inch or less. If a very perfect vacuum is required, this
operation may be repeated. On leaving the apparatus to itself
the carbonic acid which'has displaced the residual air will be
absorbed by the alkaline solution, and the aqueous vapour will
afterwards be absorbed by the sulphuric acid.
Evidently the only limit to the completeness of the vacuum
obtained in this way arises from the difficulty of obtaining carbonic acid perfectly pure from atmospheric air.
The number of asteroidal planets discovered between Mars
and Jupiter is now so large that an improved symbolical notation has become necessary, and has been agreed upon by
several European and American astronomers-viz: a circle
enclosing the number of the planet in the order of its discovery.
The number hitherto discovered is fifteen, of which five have
been discovered since the beginning of the year 1850.
Reptiles in the Old Red Sandstone.-Considerable interest
has been excited among geologists, by the announcement of the
occurrence of the remains of two or more reptiles in the old red
sandstone of Scotland, inasmuch as no vestiges of animals of a
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