The author, in presenting results relating to the decennial period derived from observations made at Trevandrum during twenty-two years, has sought a redetermination of the mean duration of that period, as shown by preceding magnetical observations connected with his own. The relation of the frequency and area of sun-spots to the amplitude of the diurnal movements of the magnetic needle gives an increased value to this investigation.

The author referred to the papers written on the subject, beginning with that by Dr Macculloch, in the year 1817; and he explained the various theories suggested.

He intimated his adoption of the Lake theory, and expressed his adherence to the view he took in the memoir read by him in this Society in the year 1846, that the blockages of the lakes had been effected by detrital matter.

It has been well said that the transmission of force is an “essential condition in machinery.” It is no less true that directness in transference is important; that the fewer links in the chain binding driver and follower together, the less likely is the machine to be put out of gear. There is no question here as to the comparative values of the different modes of conveying motion from a prime mover,—rolling contact, sliding contact, wrapping connectors, or linkwork. Each has its own excellencies; each its special advantages; and one is to be preferred to another only according to the nature of the work to be done.

Mr David Milne Home gave in the Third Report of the Society's Boulder Committee, from which the following are extracts :—In November 1875, on the invitation of Sir John Douglas of Glenfinnart, the Convener went to visit him at that place, to have an opportunity of examining several remarkable boulders reported to the Committee as situated in that part of Argyllshire.

The theorem itself may be considered obvious, and is easily applied, as I showed at the late meeting of the British Association, to prove that in passing from any one double point of a plane closed curve continuously along the curve to the same point again, an even number of intersections must be passed through. Hence, if we suppose the curve to be constructed of cord or wire, and restrict the crossings to double points, we may arrange them throughout so that, in following the wire continuously, it goes alternately over and under each branch it meets. When this is done it is obviously as completely knotted as its scheme (defined below) will admit of, and except in a special class of cases cannot have the number of crossings reduced by any possible deformation.

During the present session I propose to lay before the Society several papers on subjects connected with the deposits which were found at the bottom of the oceans and seas visited by H.M.S.Challenger in the years 1872, 1873, 1874, 1875, and 1876.

This genus was instituted by the author for the reception of the Pygopterus Greenockii of Agassiz, and characterised in the “Annals and Magazine of Natural History” for April 1875. It differs from Pygopterus in the form of the scales of the flank, which are much higher than broad, and having their articular spine arising from the whole, or nearly the whole of the upper margin; in the structure of the pectoral fin, in which all the rays are articulated for the greater part of their extent; and in the form of the anal, which is in shape like the dorsal, and is not produced backwards in the peculiar fringe-like manner characteristic of Pygopterus.

The exceedingly beautiful bird now on the table was forwarded to me on the 1st of September last by Mr Wilson, Edington Mains, Chirnside, Berwickshire. It had been shot two days previously. Mr Wilson says, “On comparing it with all the Waders figured by Bewick (the only work of the kind which I possess), I find none that correspond; whence I infer that it is really a rara avis.” He adds, “When noticed by the edge of the pond by my children it had a young one with it, which they saw it feeding. The young one, they said, was much lighter in its plumage, but was old enough to fly strongly.” The note led me to expect a full-grown female wader and young one. But the size of the bird and its general features of maturity showed it to be a male, in full winter plumage. Its companion, described as young, doubtless from its size, seems to have been the female, or reeve, which is little more than half the size of the male. In this respect the ruff differs from most of the sub-family Tringinæ, in which the females are generally larger than the males.

Body fusiform, sometimes rather deep; median fins large, the caudal deeply cleft, inequilobate; dorsal and anal triangular, acuminate, the dorsal situated nearly opposite the interval between the ventrals and the anal; base of ventrals not extended; pectoral rays articulated (except a varying amount of the commencement of the principal ones). Fin rays ganoid, closely set, striated; fulcra closely set, minute. Scales sculptured, of moderate size, rhomboidal, their posterior borders frequently denticulated or serrated; the anterior overlapped area very narrow, reduced to a mere margin. Suspensorium very oblique; gape extensive; operculum well developed, oblong; interoperculura square-shaped; no suboperculum. Branchiostegal rays numerous; the anterior one of each lateral series broader than the rest a median lozenge-shaped plate in front.