The author exhibited two instruments, both founded upon the same principles, for measuring the quantity offire-damp present in a coal mine. The first instrument consists of a tuning-fork fixed above the open end of a resonating tube, whose other end is closed by a piston whose position (read off on a scale) regulates the length of the resonating tube. The length of the tube, which resounds to the definite pitch of the tuning-fork, depends upon the nature of the gas with which it is filled. The more fire-damp, the longer is the tube. Barometric pressure has no effect upon this instrument.

It is commonly said that there is a resistance to a current at the surface of contact of a solid conductor and an electrolyte. Some good authorities, however, say that we have as yet no proof of this, as the effects observed may be due to polarisation. It is obvious that, if the reverse electromotive force due to polarisation contain a term directly proportional to the strength of the current, the ordinary methods of measurement would not enable us to distinguish this from the surface resistance above mentioned.

The accepted theory of the telephone represents that the vibrations of the sending plate to and from the pole of the magnet before which it is fixed is the origin of the currents generated in the pole bobbin of wire, and that these currents transmitted to the receiving telephone produce corresponding to-and-fro excursions of its plate. This theory, which is that of the inventor, may be shortly designated, in the happy words of Sir William Thomson for a kindred action, the push-and-pull theory. We have had in this session of the Society two communications of a practical nature, which seem directly confirmatory of this view.

This paper treats of the physical influences which promote the secretion of urine, as far as can be demonstrated by experiments upon animal membranes and the kidneys of animals recently killed. Before going on to consider the subject I may be permitted simply to mention the theory held regarding the means by which the kidney performs its function, and also say a word or two in connection with the structure of that organ. As regards its histology the kidney may be said to be composed of two elements—(1) the blood-vessels, and (2) the tubuli uriniferi. (This is leaving out of account the lymphatic arrangement.) The kidney receives its supply of blood from the renal artery, which, as it passes into the substance of the kidney, penetrates the cortical portion and gives off branches.

There are several well-known methods of mixing colours, such as the superposition of two spectra or of different parts of the same spectrum—the method of reflection, Czermak's modification of Schemer's experiment, the use of rotating disks having coloured sectors, and the direct mixture of coloured powders or coloured liquids. In all of these cases the effect may be seen with one eye, and is due to the action of light on a definite portion of one retina. But may sensations of mixed colours be produced by binocular vision of the components ? Regarding this question various well-known observers have arrived at completely opposite results.

In this paper the author first sketches the history of Rhizodus, from its discovery by Ure of Rutherglen to the most recent papers on the subject.

Placed by Agassiz among the “Coelacanthi” (i.e., cycliferous Crossopterygia of modern nomenclature) it was classified by Professor Huxley in the cycliferous division of his family Glyptodipterini, along with Holoptychius, Glyptolepis, Dendrodus. The discovery by the author, in 1875, of its subacutely lobate pectoral fin revealed the fact that it was much more closely allied to Rhizodopsis than to Holoptychius, and that it ought, along with the former genus, to be classed in a family (Cyclodipterini) distinct from the acutely lobate Holoptychiidae. The author does not consider the identity of Leidy's genus Apepodus with Rhizodus as proved.

The author proceeded with his anatomical description of the respiratory, circulatory, and pneumatic systems in this remarkable fish; referring to the differences that exist in the male, the female, the young, and the adult specimens. He also shortly noticed the alimentary and other viscera of Organic life.

Dr Handyside illustrated his paper by 24 additional drawings—including 7 microscopic views—of structure in this fish.

Since the last Report was drawn out and laid before the Society, the Convener has had an opportunity of inspecting a considerable number of boulders not mentioned in previous Reports. Some of these are interesting, on account not only of size, but also of shape, marks on them, and position. The Committee consider that advantage will result from a special description of these, and from woodcuts of a few.

1. In presenting a Fourth Report from the Society's Committee on Boulders, I may be allowed, first, to refer to the main object for which the Committee was appointed.

It was to collect data which might help towards a solution of the problem, by what agency boulders in Scotland had been transported from the parent rocks to the positions they now occupy.

The Transactions of the Society contain numerous papers by eminent geologists on this question.

The telephone is of no use as a “far-speaker,” without some means of calling the attention of the attendant at the distant station. Nothing could well be better than the “electric-bell call,” and the sounder which I am about to describe makes no pretensions of competing with the bell, except on the points of simplicity, cheapness, and facility of use; and although its employment is limited to short length lines, it may be assumed that it is upon short length lines that the telephone will be most frequently used. I have had this sounder in experimental use for more than three months, and have shown it to many persons as a very obvious expedient. However, as it does not appear to have been referred in any publication, I venture to bring it as a Note before the Society; it is of too trifling a nature to be made the subject of a formal paper.

Dr M'Kendrick stated, that by applying the microphone or carbon-interrupter of Hughes to the membrane of a phonograph, he had succeeded in using the latter as a transmitting instrument. With such an arrangement, speech could be heard in the distant telephone even after it had become inaudible near the phonograph. He also mentioned that a tambour of Marey, used in physiological experiments, spoke distinctly when the fine point at the end of the lever was applied to the marks on the tinfoil of the phonograph. When a tube was carried from the tambour to the ear, distinct speech could be obtained from phonographic tracings on copper foil, which were scarcely perceptible to the eye.

Following out a suggestion made by Mr Seabrook in Nature of May 30th, I mounted the three carbon blocks of Professor Hughes' microphone on, not as Mr Seabrook recommends, a plate of 3 inches diameter, but on a ferrotype plate about 6 inches by 4. This plate formed part of the top of a box, thus—

In the former paper on this subject, the authors stated that when hyposulphite (thiosulphate) of trimethyl-sulphine is heated to about 135° C., it loses sulphide of methyl to the extent of 23·58 per cent., the salt at the same time fusing to a clear colourless liquid. On cooling, this solidifies to a hard, very hygroscopic crystalline mass.

By the help of the phonograph we have continued the investigation described in a previous Communication (Proc. R.S.E., p. 582), and have now obtained about two hundred magnified traces of the phonographic records of vowel sounds spoken and sung by various voices, and of these sixty-five have been already subjected to harmonic analysis, extending as far as the sixth partial tone. In each case the results have been accepted as satisfactory only when, after the magnified trace had been obtained, the record on the tinfoil of the phonograph still gave the vowel sound satisfactorily. Our attention has hitherto been almost exclusively directed to the vowels u (the vowel sound in “food,”) and o (as in “oh,”) both of which are well spoken by the phonograph.