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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.

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b.

(CH3)2S, CH,HS.

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

(CH2),Se', (CH,),Se, (CH ̧),S.

(CH ̧),S, (CH ̧),Se, (CH),S.

(CH),S, CH,HSe.

(CH),S, (CH).S, (CH ̧)¿Se .
(CH),Se, 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.

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represents a couple of ovals linked together.

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

have

10

or

ABCD A DCEFD FEBA|F

2r3+3r2
31

Of course such figures can be transformed or deformed according to the methods given in my first paper-the scheme and the typesymbol alike remaining unaltered. And alterations of both scheme and symbol are, in various classes of cases, producible by the processes of my last paper without any change of links or linking.

The genesis of the scheme of a link may be most easily studied by forming a knot into a link. This is done by cutting both turns of the wire at any junction, and joining them again so as to make two closed curves instead of one. No intersections are lost by this process, except that which was cut across, provided, of course, that the original knot had no nugatory intersections, and that none are rendered nugatory by the operation of cutting the whole across. Any crossing with four adjacent crossings when the turns of the coil pass alternately over and under one another will appear in a scheme as follows:

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implying that from X through B and C back to X forms one continuous circuit; similarly from X through D and A back to X.

There are but two ways in which continuity can be kept up if we cut the cord twice at X, and reunite the ends in a different arrangement from the original one.

It is obvious that if we pass from C to B, by way of X (abolished), and similarly with the rest, we divide the continuous closed curve into two separate (but generally inter-linked) closed curves. If we pass from A, by way of X (abolished) to C, we pass thence in time to B, and finally by way of D to A. Thus the curve remains continuous, but with one intersection less than at first. And, in either case, the alternate order of the signs of the crossings will be maintained throughout.

In the former of these modes we take the part containing Cand B (and we may, if we please, also take the rest) in the same order as before the change. The scheme is therefore, without any other change, simply divided into two parts, which are separated from one another by the (abolished) junction X in its two positions.

In the second mode, it is obvious that the letters in one of the two parts separated from one another by the mark X in its two places are simply to be inverted in order without change.

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