The author, after briefly stating the views of Mr Milne, and the remarks of Sir G. S. Mackenzie, gave his reasons for agreeing with the former, that the terraces were the beaches of lakes, formed by barriers across the valleys; and, with the latter, in holding that these barriers could not have been formed of earthy detritus. He then proceeded to shew that the theory of Agassiz, according to which the barriers were formed of glaciers, was the most probable yet advanced, and while it required some modification in the details to render it consistent with recently observed facts, was strongly supported by the researches of Professor Forbes, both in regard to the former existence of glaciers in our latitudes, as demonstrated in the case of the Cuchullin Hills, and in regard to the laws of the motion of glaciers, as developed in Professor Forbes's papers on the Glaciers of the Alps.

This instrument is almost a faithful reproduction of S'Gravesande's apparatus described in his “Physices Elementa Mathematica,” 1742 (but not in the previous editions). It is described or alluded to by few modern writers, except Biot in his “Traité de Physique.” It consists of a strong wooden table or frame, with a vice at each end, between which a wire or lamina may be stretched with a determinate tension by means of a weight attached by a cord, passing over a pulley in the manner of the musical apparatus, called a Monochord. After the tension is adjusted, both vices are screwed fast, the space included between them being exactly 50 inches. If now, any deviation of the middle point of the wire included by the vices be made (similar to the action of sounding a harp-string), the force required to pull it a certain distance aside will depend, 1st, on the length of the wire; 2d, on its tension; 3d, on its extensibility, or the modulus of elasticity.

The occurrence of anthracite in this locality has been noticed and recorded by several observers, who seem to have overlooked some of its more remarkable peculiarities. At present, this mineral may be detected in a series of anastomosing vertical veins of calcareous spar, including, at the same time, angular portions of the claystone porphyry in which they are situate, on the upper north walk on the north side of the Observatory. The anthracite occurs, 1. In rounded, drop-like pieces, on which the calcareous spar has been moulded, not unlike the colophonite of Norway.

The object of this communication was to bring before the Society some phenomena which are exhibited when certain liquids, denser than water, are exposed, while contained in glass or porcelain vessels, to the alternate action of acids and alkalies. The liquids with which the phenomena described were noticed, were chloroform, bisulphuret of carbon, Dutch liquid (C4 H4 Cl2), bromine, oil of cloves, of sassafras, of cinnamon, and of bitter almonds. The majority of the experiments were made with chloroform, and the phenomena presented in common by all the liquids mentioned were described in full, as presented by chloroform.

The object of this paper is to point out the extremely important and interesting characteristics of the orbit of the two stars of a Centauri round their centre of gravity, with the object of procuring as many observations as possible from southern observers during the periastral passage in 1851·5.

The substance examined by the author was imported into Glasgow from Bombay, under the name of sooranjee, as a substitute for madder, but had been found useless by the dyers. No information could be obtained regarding its botanical origin in this country, but the importers having written to their correspondents received a quantity of seeds, labelled, Seeds of the Sooranjee plant, Morinda citrifolia. These seeds did not germinate, but agreed in their characters with those of M. citrifolia; and, for reasons stated at length in the paper, are considered by Dr Balfour to belong to that plant.

The laxity of the present methods having been brought, by his friend Captain Cockburn, R.N., before the author, with a desire to be furnished with some sort of anemometer, and with some easy means of eliminating the effect of the motion of the vessel, he began to consider what would be the most appropriate form of anemometer to be used at sea; for several kinds had been already tried, but had failed, as he thought, from not being constructed on a suitable principle. The species which the author considered the best, was that which should imitate, as nearly as possible, mutatis mutandis, the log-line by means of which the ship's way through the water is determined; for that instrument seems to have preserved its situation and supremacy over all others on board-ship amongst all nations, and from the time of Columbus to the present, mainly on account of the appropriateness of the principle involved.

This communication is divided into six sections. In the first, the author states that the object of his paper is to supply a defect in the theory of chlorine-bleaching, by endeavouring to explain why the removal of water from that gas arrests its bleaching action. In the preliminary discussion, he refers at some length to Davy's theory, that moist chlorine does not bleach directly, but only in a secondary way, by combining with the hydrogen of the associated water, and liberating the oxygen, which is the true bleacher. After pointing out the untenable assumptions and self-destructive arguments on which this theory is built, the author proceeds in the second section, which discusses the influence of sunlight on the bleaching action of dry chlorine, to shew; that Davy's proposition that dry chlorine does not bleach dry organic colours is true, provided direct sunlight be excluded, but does not apply to the gas when exposed to the actinic influence of the sunbeam. In a comparative trial, one specimen of dry litmus paper was found to resist the decolorizing action of dry chlorine for more than eight months when kept in darkness; whilst the colour of another portion of the same paper totally disappeared after six weeks' exposure to sunshine.

In this communication the author details the general properties of bone-oil, the substance employed in his experiments, and those of certain of the volatile bases contained in it.

The oil was first rectified, and the product collected in two separate portions, each of which was separately agitated with dilute sulphuric acid for the separation of the bases. The acid solution so obtained was then boiled down to a small bulk for the purpose of separating any non-basic oil which might have been dissolved, and distilled with potash, soda, or slaked lime. The bases passed over in solution in water, from which they were separated by means of solid caustic potass; similar processes were performed with both portions of the bone-oil, but in the present paper the author confines himself to the pure volatile portion only.

From an experiment made in very cloudy weather, and therefore rather unfavourable light, I determined the following indices of refraction for pure chloroform, prepared by Dr George Wilson, of sp. gr.

The measure of the refracting angle of the prism was 39° 41′. References were made to the principal lines of the spectrum, as below, the temperature of the fluid was probably 54°.

The principal part of this paper was devoted to a description of alluvial terraces, as seen along the banks of the Rhine at Bonn, Mainz, and Basle, and in the valley of the Arve, the well-known tributary of the Rhone. These terraces, which rise high above the reach of the present river, yet slope in the same direction. The intermediate hollow or trough in which the river runs, has evidently been cut out of what was at first an entire sloping sheet of detrital matter, filling the valley from side to side up to a certain height. At the lower part of the Arve valley, the detrital matter has been discharged across the valley of the Rhone, so as to form a barrier for the Lake of Geneva.

As the reading of this paper was only commenced at his meeting, the abstract is deferred until the conclusion.

A large quantity of mud, dredged up from the harbour of Valetta, having been deposited on a piece of slightly-inclined ground, and having been subsequently moistened to an excessive extent by rain, and by the overflow of a neighbouring tank, the upper parts began to flow down over the lower and the original boundary, in six distinct streams; this separation being apparently caused by the difference of resistance and level of the under stratum.

Mr Strachey's letter contained some interesting observations which he has been making on the motions of the glaciers in the Himalayan mountains; and his measures, conducted on the plan of Professor Forbes in the Alps, are the earliest that have been taken in Asia. The Pinduree glacier, on which the observations were made during cold weather, was found to move 3 feet 1 inch in 5 days at the centre, and at the sides about 1 foot 5 inches.

Lieutenant Strachey's former Researches on the Glaciers of the Kumaon Himalaya (published in one of the Indian Journals), have satisfactorily proved the existence of glaciers in lat. 30° 20′, which present in detail all the phenomena of those of Europe.

A second mud-slide having occurred at Malta, with more marked features than the first, Mr Milward was enabled to ascertain that the curved bands of dark and light mud are not only accompanied by a difference of elevation in those parts, but that these wrinkles are the cause of that difference of colour; the more watery parts draining from the ridge, leave that rough, and form a smooth alluvium in the hollow.

Professor Forbes stated that Mr Milward's shrewd suspicion of the bands of ice of different consistence being accompanied also by wrinkles or elevations, had been discovered by himself some years before, at the very place and time pointed out as most likely; and he shewed that, while there is a tendency in a tenacious viscous fluid to produce wrinkles, under pressure capable of effecting detrusion, even where the supply of the fluid is uniform; that this quality is greatly increased when the supply of the fluid is by fits, as it is in fact at the head of this glacier, where the quasi-hydrostatic pressure from behind, combined with the frontal resistance, produces a thickening, or convex lip or wrinkle.

The questions to be resolved by a complete theory of the motive power of heat, are the following:—

I. What is the precise nature of the thermal agency by means of which mechanical effect is to be produced, without effects of any other kind?

II. How may the amount of this thermal agency necessary for performing a given quantity of work be estimated?

At the commencement of this paper the two following propositions are laid down:

I. That water at the freezing-point may be converted into ice by a process solely mechanical, and yet without the final expenditure of any mechanical work.

II. That the freezing-point of water must become lower as the pressure to which the water is subjected is increased.

The early history of the English air-pump has been latterly allowed to fall into great confusion, so that the steps by which the instrument was improved, the periods at which those improvements were made, and the parties by whom they were effected, are all more or less confounded with each other, or mis-stated.

It is in connection with the double-barrelled air-pump, that the accepted history of the instrument is chiefly erroneous, but the mistakes made in reference to the more complex engine, have ultimately involved in confusion even the authentic records of the steps by which the earlier single-barrelled air-pump was improved, so that the account of its successive alterations must commence with its earliest and simplest construction.

The object of this paper is chiefly one of nomenclature. Every one has felt the difficulty of describing with the precision the innumerable hues which occur in nature and in art; and which it is equally desirable for the optical philosopher, the artist, and the manufacturer, to be able to refer to in a clear and definite manner. But such a nomenclature or classification must proceed upon some admission as to the manner of compounding complex hues out of simple ones; and, therefore, the author first treats of the (so-called) Primary Colours. He admits it as highly probable, that all known colours may be formed out of Red, Yellow, and Blue; although, when we attempt to compound pigments, we have a very notable loss of light, and also an unavoidable impurity, which is most visible in the compound tints.