werden, z. B. durch Andeutungen über mögliche Bezeichnungs. methoden, Symbole und dgl. durch welche wir, wie es die Wissenschaft in allen analogen Fällen zu erstreben hat, von der Intuition zu den Begriffen fortzuschreiten vermögen. Die von mir empfohlenen Symbole sollen nichts weiter sein als ein derartiger Fingerzeig, und wenn ich auch ganz mit Ihnen darin übereinstimme dass das Schema einen Nodalcomplex leichter construirbar macht als das Symbol, so bleibt doch das Schema viel weiter von dem Begriffe entfernt als das Symbol, auch abgesehen von den auf beiden Seiten noch übrig bleibenden Vieldeutigkeiten. Wie fragmentär das, was ich vor 30 Jahren darüber angedeutet habe, gewesen, kann ich Ihnen unter vielen an dem einen Punkte erläutern, dass ich mich dort nur auf die Verknotung einer einzigen cyklischen oder einer cyklodischen Curve beschränkte, und nur auf solche Verschlingungen unter der Benennung 'reducirt' einging, deren sämmtliche Parcellen (incl. Amplexum) monotyp sind, wiewohl Ihnen selbst bekannt ist, dass es Knoten giebt mit Maschen, deren Ecken promiscue & und λ heissen, ohne auf einfachere Formen, d. h. eine geringere Zahl von crossings reducirbar zu sein.

Es versteht sich von selbst, das die in den Vorstudien angeführten Symbole nur auf monotype reducirte Complexe anwendbar sind, und durch Verallgemeinerung andere Gestalten annehmen, worauf ich indessen hier weiter einzugehen unterlasse."

I have thought it better to give Listing's own comments on my remarks than to seek permission from the Council to alter these remarks in the text.]

Monday, 19th February 1877.

DAVID STEVENSON, Esq., Vice-President, in the
Chair.

The Chairman reported that the Council had awarded the Makdougall-Brisbane Prize for the biennial period 1874-76, to Alexander Buchan, M.A., for his paper "On the Diurnal Oscillation of the Barometer," which forms one of an important series of Contributions by Mr Buchan to the Advancement of Meteorological Science.

The following Communications were read:

1. On the Action of Sulphuretted Hydrogen on the Hydrate and on the Carbonate of Trimethyl-sulphine. By Professor Crum Brown.

(Abstract.)

The investigation, of which this paper contains the first part, was undertaken with the view of throwing light on the constitution of salts of trimethl-sulphine.

These salts have been represented in two different ways-1st, as compound of tetratomic sulphur, and 2d, as molecular combinations of sulphide of methyl with methylic ethers, just as the ammonia salts have been represented as compounds of pentad nitrogen, or as molecular combinations of ammonia with hydric salts.

VOL. IX.

2 U

It appeared to the author that facts having an important bearing on the question, which of these is the better representation of the constitution of such bodies, might be obtained by the study of the sulphur compounds of trimethyl-sulphine, of the corresponding selenium compounds, and of the intermediate substances.

The following list, in which each substance is formulated-a, on the assumption of tetrad sulphur and selenium, and b, on the supposition of molecular union illustrates this idea.

b.

(CH,)2S, CH,HS.
(CH3),S, (CH)„S, (CH ̧),S.
(CH),Se, CH,HS.

(CH),Se', (CH),Se, (CH),S.

(CH ̧),S, (CH ̧)„Se, (CH ̧)„S.

(CH),S, CH,HSe.

(CH),S, (CH),S, (CH),Se.
(CH),Sе, CH,HSe.

(CH3),Se, (CH),Se, (CH),Se.

(CH ̧),S, (CH ̧),Se, (CH ̧),Se .

Of these it is obvious that (3) and (6), (5) and (7), and (4) and (10) form three pairs of isomers.

Upon any theory (3) and (6) may be expected to be different, but it is not so with the other two pairs. They ought to be different, if the assumption of tetrad sulphur and selenium is correct, but on the theory of molecular combination it is difficult to see how a difference of properties could be accounted for.

The hydrate and also the carbonate of trimethyl-sulphine are readily acted upon in the dry condition by sulphuretted hydrogen, and the product is colourless if air has been rigidly excluded. The characteristic reaction with nitroprusside shows the product to be a sulphide or sulphhydrate, but the action of oxygen upon it is so rapid that it has not yet been obtained in a condition fit for analysis. Before attempting to prepare it in a state of purity, it was thought best to examine the products of its oxidation. These are-(1), an orange polysulphide, which in the presence of moisture

and oxygen is further oxidised, with separation of yellow sulphur, yielding (2) hyposulphite of trimethyl-sulphine.

The action is thus similar to that of sulphuretted hydrogen on potash or carbonate of potash, but takes place with much greater rapidity.

The examination of the sulphide and polysulphide of trimethylsulphine will form the subject of the next part of the paper.

2. On Links. By Professor Tait.

(Abstract.)

Though in my former papers on knots I have made but little allusion to cases in which two or more closed curves are linked together, the method I have employed is easily and directly applicable to them. I stated to the British Association that the number of intersections passed through in going continuously along a curve, from any intersection to the same again, is always even-whether it be linked with other curves or not Hence, even when a number of closed curves are linked together, the intersections may be so arranged as to be alternately over and under along each of the curves.

When this is done, each of the meshes has all its angles right or left handed; so that Listing's type-symbols may be employed, just as for a single knotted curve. The scheme, however, consists of as many parts as there are intersecting curves-each part containing, along with each of its own crossings twice, each of its intersections with other curves once.

represents a couple of ovals linked together.

When three ovals are joined, so as to form an endless chain, we have

or

ABCD|A DCEF|D FE BA | F