leaves it to the clinical observer to experiment on man with such substances as sodium benzoate, sodium salicylate, baptisin, euonymin, sanguinarin, &c., and thereby to ascertain whether or not these substances also stimulate the human liver; and of necessity it is also left to him to ascertain in what diseased state the employment of this or of that substance is most advantageous.

Other general conclusions have been already stated at the close of Part I.

2. On a New General Method of Preparing the Primary Monamines. By R. Milner Morrison, D.Sc.

3. On the Preparation and Properties of Pure Graphitoid and Adamantine Boron. By R. M. Morrison, D.Sc., and R. Sydney Marsden, B.Sc.

4. On Colour in Practical Astronomy, spectroscopically examined. By Professor Piazzi Smyth.

Monday, 1st July 1878.

SIR WYVILLE THOMSON, Vice-President, in the Chair.

The following Communications were read :

1. On the Disruptive Discharge of Electricity. By Alexander Macfarlane, D.Sc., and P. M. Playfair, M.A.

(Abstract.)

During the months of May and June of this session, we have endeavoured to investigate certain questions suggested by our experience of the discharge of electricity through the gases and through oil of turpentine.

Ordinary paraffin-oil, when used as a dielectric, exhibits the same phenomena as oil of turpentine. Gas is liberated by the passage of the spark, and at the same time carbon is deposited. Once produced, the gas bubbles make the passage of the spark more easy through bringing the electrified surfaces nearer to one another; hence,

in taking a series of observations, it is necessary to get rid of the bubbles after the passage of each spark. They were attracted generally to the positive surface, but sometimes to the negative. The attraction was more marked when no jars were attached to the Holtz; it was not so powerful as in oil of turpentine, and was generally in the opposite direction.

The electrostatic force required to pass a spark through a layer of paraffin oil or of turpentine is constant, whereas it is variable in the case of air and other gases. For the observed differences of potential plotted with respect to the thickness of layer give a straight line through the origin, while in the case of the gases the curve is concave.

The electric strength of the paraffin oil used was found to be 4, of the turpentine 37; air being unity.

To investigate the effect upon the electric spark of heating the electrodes, we constructed electrodes of thick platinum wires placed at right angles to one another-a suggestion we owe to Professor Clerk Maxwell. When one of the wires was heated by a current from a battery of four Bunsen elements, the electrometer deflection was diminished by about one-fourth of its amount, and that whether the wire heated was positive or negative. A similar diminution was observed when the deflection for continued sparks was taken. This diminution of the difference of potential must be due to change at the surface of the wire; for the air between the wires (the shortest distance between the wires being 4 millimetres) cannot be so much rarefied by the heating of the wire as to produce the effect.

We have also investigated the effect upon the electric spark of heating the air round the discs, the pressure being kept constant. We have observed the deflections of the electrometer for a constant spark for temperatures from 20° C. to 280° C., and find that they indicate a curve, which slopes down gradually as the temperature is increased, while the deflections during cooling give a curve which is somewhat lower at the lower temperatures.

It appeared an important matter to ascertain whether the electrometer used in all these observations gives deflections strictly proportional to the inducing charge. To calibrate it by means of cells would have required a very large number; hence the following

on.

method suggested by Professor Tait was adopted. A charge was put upon the inducing ball of the pair on the stand, and the deflection read; the charge was then divided by bringing an equal ball into contact with the inducing ball, the deflection read, and so The deflections were so nearly halved each time, that we may infer that they are strictly proportional to the charge on the inducing ball. We had arranged to verify our former observations in this matter last Thursday forenoon (27th June); but as the deflection on the scale always fell in the negative direction, and went to a great distance beyond the proper zero when the dividing ball was brought into contact, we gave it up. This effect was, doubtless, due to a strong negative electrification of the air; for the thunderstorm came on immediately.

2. On the Wave Forms of the Vowel Sounds produced by the Apparatus exhibited by Professor Crum Brown. By Professor Fleeming Jenkin, F.R.S., and J. A. Ewing, B.Sc. At a recent meeting of the Society, Dr Crum Brown exhibited a gutta percha bottle of irregular form, which, when applied as a resonance cavity to reeds of various pitches, gave very good imitations of certain vowel sounds. By closing certain apertures in the side of the bottle it could be made to say A ("father"), A (" awe"), O ("oh"), and I ("machine"). When the cavity was kept constant, and the pitch of the reed was altered, the same vowel continued to be given. Dr Crum Brown was good enough to lend us the apparatus, in order that we might investigate the sounds given by the bottle in the same way as we have been investigating certain human vowel sounds, by obtaining and magnifying phonographic traces, and then subjecting them to harmonic analysis as far as the sixth partial tone. Of the vowels which the bottle speaks, O is the only one which we have fully examined in this way when spoken by the human voice, and we have confined our attention to it among the artificial vowels also.

By using reeds of various pitches we have obtained curves or traces of the artificial O's sufficiently good for harmonic analysis on the following pitches-e, f, g, b, c', e'b, and e'. The pitch was in each case determined by measuring the length of the traces. The

vowel quality of the sounds, as repeated by the phonograph, was exceedingly good, even better that the original sound, as the jarring noise of the reed was lost. The sounds were thoroughly recognis able as O, of perhaps a somewhat bright species. The table below shows the amplitude of the successive partial tones, along with their absolute pitch to the nearest semitone.

It cannot be said that these figures show any specially strong resonance on or close to bb', which Helmholtz gives as the proper tone of O, but they do show a wide range of resonance, extending a long way above and below that pitch. There is distinct reinforcement as high as g′′, or even g", and as low as e', if not lower, and partial tones falling anywhere between these limits are more or less reinforced.

The above analysis appears to show that a strong resonance on or near bb' is not essential to O, and that this vowel effect may be satisfactorily produced by other joint resonances above and below that pitch.

In a previous communication we pointed out that if the view be adopted that the constituents of the O's, sung at various pitches by a human voice, are due to the reinforcement caused by a constant oral cavity, the results of our analyses showed that this cavity not only has the property of strongly reinforcing tones close to bb', but must also be capable of strengthening, more or less, tones widely distant from that pitch, and extending over a large range. The analysis of the artificial O's now shows that a constant cavity may possess the latter property in quite a sufficient degree.

In order, however, to test this still further, we made the following experiment. A tube consisting of a piece of cane of the same size as one of the reeds was put into the neck of the bottle in place of the reed, and the side apertures of the bottle were closed so as to arrange the cavity for the vowel sound O. The end of the tube was then inserted in the ear, so that the whole apparatus acted as a resonator to sounds from outside. Then, striking the keys of a piano in succession, we observed what notes gave the peculiar humming effect due to reinforcement by the resonator. On working down the scale the resonance first became appreciable on g'. It then got stronger and stronger down to f" and e", which were both intensely and nearly equally strong. eb" and d" were a little weaker, but still very strong, and on the resonance again became very intense. c" was a little weaker, but also very strong. The resonance continued as the pitch fell, being sometimes stronger and sometimes weaker. g' and f were both strong,-decidedly stronger than could be accounted for by the reinforcement of their second partials g' and f". ƒ' was weaker,—so much so that the resonance observed on it might be due to the second partial.

The presence of the upper partials in the notes struck made this method of testing the resonant qualities of the cavity inapplicable to pitches below those named. But the above cases, in which the reinforcement was distinctly of the prime, sufficed to show that the cavity would strengthen any tones between g" and f, at least, some more and some less strongly, while they left it an open question whether there was not resonance down to a lower limit of abso

lute pitch. Of course, it is to be observed that the bottle, when applied to the ear in the manner described, might differ in its resonant peculiarities from the same bottle applied to a reed, but its range is probably as great in the former case.

When the bottle was arranged for the vowel sound A, and tested in the same way, the resonance was perceptible as high as e"", and the highest maximum occurred on c'". In this case also there was reinforcement over a range of at least an octave.

Traces of the wave forms of the artificial O's spoken of in this paper will be given along with those of other O's when the full account of our work is printed.

VOL. IX.

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