Last summer I communicated a paper to the Society on an Iodine Cell. This cell consisted of a carbon and zinc rod immersed in solution of iodine, in iodide of potassium. I found that iodide of zinc was equally suitable to dissolve the iodine in, as mentioned in that paper. While experimenting with this cell, the idea occurred to me of using it as a secondary battery. When the cell is exhausted, the whole of the iodine has combined with the zinc to form iodide of zinc. If an electric current is passed into this exhausted cell, the iodide of zinc is decomposed, zinc being deposited on the zinc plate, and iodine being set free at the carbon plate. The cell is now ready for use, and will give a steady current, having an EMF of 1·2 volts until the iodine is again combined with the zinc. I tried several experiments on this cell in Newcastle, with a view to testing its applicability to electric lighting as a storage battery.

The Convener being now no longer able to climb hills, or walk to any considerable distance, his own contribution of information to the Committee is, this year, exceedingly small.

The only place visited by him during last autumn was East Loch Tarbert, Loch Fyne, at the suggestion of Mr. Alexander of Lochgilphead, whose services to the Convener during the two previous years were peculiarly valuable.

Origin and Objects of the Committee appointed by the Royal Society of Edinburgh to obtain information regarding Boulders in Scotland.

The subject was brought before the Society by Mr. Milne Home in a paper referred to in the following Minute of Council, dated 21st April 1871 :—

“The Council, whilst authorising Mr. Milne Home's paper “On the Conservation of Remarkable Boulders in Scotland,” to be read at an ordinary meeting of the Society, agree, in compliance with a suggestion in the paper, to express approval of its object, and of the scheme proposed for carrying it out.

In this paper the author enunciates and illustrates the following propositions:—Speech is produced by distinctly separate jets of breath emitted under pressure; each such jet he names a monopressure. A monopressure may be used for the utterance of a single syllable, which may consist of a single vowel, or a vowel preceded or followed, or both, by consonants. In a monopressure the sound is weaker at the beginning and end, and stronger in the middle. The weak beginning, or the weak ending, of a monopressure, or both, may be used for the utterance of an unaccented syllable. There are thus four forms of a monopressure:—monosyllabic; dissyllabic, with the accent on the first; dissyllabic with the accent on the second; trissyllabic, with the accent on the second.

In his recent lectures on Solar Physics, Professor Stokes, while expounding his theory of the connection of magnetic disturbances, auroræ, and earth currents, says:—“We might not have tension enough to produce such a discharge (that is, a flash of lightning), the resistance to the passage of electricity from one portion of the air to another, which at any rate would be comparatively dry compared with what we have in warm latitudes, would prevent it by itself alone.” Professor Stokes subsequently remarked in a letter to Nature: —“These words, without actually asserting, seem to imply that the resistance to such a discharge through moist air would be less than through dry. My attention has been called by a friend to the fact that it has been found by experiment that moist air insulates as well as dry. I have not met with experiments tending to show whether the resistance to a disruptive discharge is the same or not in the two. Be that as it may, it does not affect what follows; for we know, as a fact, that thunderstorms are absent in high latitudes.”

Professor Chrystal, in his article on “Electricity” in the Encyclopœdia Britannica, mentions the following formula of Sir William Thomson's, connecting the heats of combination in a voltaic cell with the EMF of the cell.

(Where E = EMF of the cell; J = Joule's equivalent; e = amount of zinc, dissolved by unit current in unit time; θ = heat of combination of one grm. of the metal in the cell.)

This formula has been tested for the Daniell and other cells.

It occurred to me that it was peculiarly applicable to the cuprous chloride cell and to the iodine cell recently described to the Society, on account of the simplicity of the reactions in both these cells, and that it could in this way he used as a simple method for the determination of the heats of combination of the metals with the halogens, by determining their electromotive forces, as the active elements in one or other of these cells. Mr. Burton and I accordingly set to work to investigate the matter.

The series of experiments here described had for their object the measurement of the variation in the Peltier effect due to change of temperature; they were made during the last six weeks. The arrangement which I used in these experiments was suggested by a form of apparatus used in Professor Tait's laboratory; the following is a description of it. A plate of sheet lead (say) is bent into the shape of an arch (∩-shaped), and to its lower edges are soldered two plates of sheet-iron, to the opposite edges of which are soldered three or four copper wires proceeding to mercury-pools, which can be put into connection with a battery.

At the meeting of 17th April we gave an account of some experiments made at the request of Professor Tait on the lowering of the maximum density point of water by pressure. We called the notice we gave of these experiments at that time preliminary, because we were anxious to perform further experiments to satisfy ourselves thoroughly of the correctness of the important conclusions then arrived at. We desire now to state that we have repeated these experiments with some slight improvements in experimental details, and at different temperatures, and are glad to state to the Society that our further experiments quite bear out the conclusions previously arrived at. The following will suffice to show the nature of any day's experiment. [For description of the apparatus used, &c, see ante, p. 626.]

In this paper the author discusses the mechanism of speech, and the character of the vowels and consonants which occur in the English language. He points out the importance of attending to the proper division of words into syllables, and of clearly articulating consonants. He shows how his theory of monopressures facilitates the correct reading of poetry.

If we assume the lowering of the temperature of maximum density to be proportional to the pressure, which is the simplest and most natural hypothesis, we may write

where p is in tons-weight per square inch.

Now Thomson's thermodynamic result is of the form

This becomes, with our assumption,

As the left-hand member is always very small, no sensible error will result from integrating on the assumption that t is constant on the right (except when the quantity in brackets is very small, and then the error is of no consequence).

The angular rotation of the plane of polarization of light-rays in their passage through quartz is a function of the wave-length, and is roughly represented by the formula

where A is a constant depending on the quartz. This formula is only approximate, however, and one object of the experiments described below was to ascertain how closely the rotation might be represented by three terms of the equation

When a salt, such as sodium chloride, which crystallises at ordinary temperatures without water of crystallisation, is dissolved in water, contraction takes place; that is, the specific gravity of the solution is greater than that calculated for a solution of that strength from the specific gravity of the salt in the solid state and that of water, by the formula—

Where—