ly 10 inches percolate into the rock, the supply of water stored up by
the Permian and New Red formations was estimated by the committee to
amount to 140,800,000 gallons per square mile per year. This rate would
give, for the 10,000 square miles covered by the formations, in Great
Britain, 1,408,000,000,000 gallons. Only a very small proportion of this
amount is made available for the supply of cities and towns.

The subject of the chemical constitution of matter was taken up by Mr.
Johnstone Stoney, F. R. S., who amused and interested the chemical
section by a number of drawings of tetrahedra, octahedra, etc., on to
which he dexterously stuck representations of oxygen atoms, chlorine
atoms, and so on. His general endeavor seemed to be to convince his
auditors that in most basic salts oxygen is divalent, being in direct
combination with the acidifying constituent of the molecule, but that
when oxygen is not so directly related to this constituent in basic
salts it is tetravalent.

In the geological section, Dr. Bryce observed that there are two lines
along which earthquakes are commonly observed in Scotland, the one
running from Inverness, through the north of Ireland, to Galway bay, and
the other passing east and west through Comrie. The phenomena of
earthquakes in the latter district are now being systematically
observed and recorded, under the direction of a committee appointed by
the British Association, seismometers being employed on the two
principles of vertical pendulum and delicately poised cylinders.
Arrangements have been made to ascertain whether shocks in this region
can be traced to any common central point, there being reason to believe
them to be connected with a mass of granite in Glen Lednoch, whose
position was indicated on a map exhibited by the author. He thought the
Comrie earthquakes may be explained on Mr. Mallet's theory of a shock
produced by the fall of huge masses of rock from the roof of huger
caverns in the earth's crust.

In a paper on the plants of the coal measures, Prof. W. C. Williamson
expressed his strong conviction that the flora of the coal measures
would ultimately become the battlefield on which the question of
evolution with reference to the origin of species would be fought out.
There would probably never be found another unbroken period of a
duration equal to that of the coal measures. Further, the roots, seeds,
and the whole reproductive structure of the coal-measure plants