Volume 23 — BRITISH ASSOCIATION NOTES.

The committee appointed to test experimentally Ohm's law, that with any conductor the electromotive force is proportioned to the current produced, reports that this law is absolutely correct. If a conductor of iron, platinum, or German silver of one square centimetre in section has a resistance of one ohm for infinitely small currents, its resistance when acted on by an electromotive force of one volt (provided its temperature is kept the same) is not altered by so much as the millionth of a millionth part. This fine result is the more gratifying since Ohm's law is entirely empirical and does not rest at all upon logical deduction.

The vast amount of water circulating through the solid earth is shown by the calculations of the committee on the underground waters of the Permian and New Red sandstones.

Taking an average rainfall of 30 inches per annum, and granting that only 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 are all present in an unequalled state of preservation. With reference to calamites, Prof. Williamson said that what had formerly been regarded as such had turned out to be only casts in sand and mud of the pith of the true plant. He had lately obtained a specimen of calamite with the bark on which showed a nucleal cellular pith, surrounded by canals running lengthwise down the stem; outside of these canals wedges of true vascular structure; and lastly, a cellular bark.

In the department of anthropology, Dr. Phené read a paper "On Recent Remains of Totemism in Scotland." He defined Totemism as a form of idolatry; a totem was either a living creature or a representation of one, mostly an animal, very seldom a man. It was considered, from reference to Pictish and other devices, that a dragon was a favorite representative among such people of Britain as had not been brought under Roman sway.

Mr. W. J. Knowles read a paper "On the Classification of Arrowheads," recommending the use of the following terms: stemmed, indented, triangular, leaf-shaped, kite-shaped, and lozenge-shaped. Commander Cameron, the African explorer, mentioned that arrow-heads of the same shape as many exhibited by Mr. Knowles were in use in various African tribes. One shape was formed so as to cause the arrow to rotate, and was principally used for shooting game at long distances. The shape of the arrows varied according to the taste of the makers; in one district there were forty or fifty different shapes.

Commander Cameron gave drawings of the men with horns, a tribe of which has been found by Captain J. S. Hay. According to the reproductions of these drawings by the illustrated papers, these horns are very prominent, and project forward from the cheekbone.

Mr. Gwin-Jeffreys, whose experience in deep-sea dredging makes his opinion valuable, said that telegraph engineers did not sufficiently take account of the sharp stones on the sea bottom, but assumed too readily that they had to deal with a soft bottom only.

Mr. John Murray of the Challenger expedition announced that meteoric dust is found in the sea ooze, a result that follows as a matter of course from the discovery that this cosmic dust is falling all over the earth.