The author, after noticing the fishes in which an electrical apparatus had been discovered, stated that, with the exception of Geoffroy St Hilaire, no writer had endeavoured to shew that Skates possessed electrical organs. The organ to which that writer alluded, the author regarded as nothing else than muciparous ducts, identical with the very same organs in the Torpedo, and quite distinct from the electrical organs. The circumstance was then mentioned which directed the author's attention to the tail of the skate, and led him to suppose that an electrical organ might exist in it.

The idea suggested in this paper, occurred to the author three years ago, from reflecting that the destruction of spherical aberration in the eye might be effected by a modification of the curvature of the lens, as well as by the variable density which it is known to possess, and which has usually been accounted for as intended for that purpose.

The author considering the probability to be almost infinite against the sphericity of the surfaces (a necessary evil in our instruments, but inexplicable in a natural organ), a conviction which he afterwards found to be reduced to certainty by experiments which have actually been made on the figure of the lens—he conceived that the variable density of this part of the eye must have some other cause.

This beach presents the appearance of a terrace, extending along the north side of the Carse of Stirling, from the foot of Abbey Craig westward to Lecropt Church, and beyond it. Its length is about two miles; its breadth, at Lecropt Church, is about 200 feet, at Airthrey Mineral Well 900 feet, and at Airthrey Castle near half a mile. Its upper surface is nearly a dead level in both directions, except where breaches have been made in it, by streams or other agents. The elevation of this surface above the Carse in about 85 feet, and above the Forth at Stirling probably 110 feet. Rock is seen under the terrace at the village of Causeyhead, in the bed of the River Allan, at the Bridge, and at the bottom of the acclivity under Lecropt Church.

The author first described, generally, the appearance of the loose materials covering the surface; and referred to some districts in the north of Scotland, especially the central one on the borders of Perth and Inverness shires, as demonstrating the effects of vast currents of water having passed over the surface. He also referred to the valleys of the river Conan and its tributaries, in Ross-shire, as presenting an epitome of all the phenomena which may be supposed to result from a vast flood gradually subsiding, and taking the direction of the valleys. He then shortly alluded to the theories proposed to account for the present condition of the surface, which appear to resolve themselves into the effects of a remote cause.

The observatory is situated on a rising ground forming the left bank of the Tweed, and is at a distance of about fifty yards from the Astronomical Observatory. It is built of wood; copper nails were used, and all iron carefully excluded from the building.

The plan of the observatory is rectangular, 40 feet long by 20 broad: It is divided into one large room to the north, 40 feet by 12, and two ante-rooms to the south, with the lobby and entrance doors between.

The instrument described in the paper is made of German silver, and is about a foot in length, and of an inch in breadth; along the middle of it there is a groove for a slider. On the right edge of the groove is engraved a scale of inches, and on the left the degrees of temperature from 0° to 85° Fahrenheit, each being placed exactly opposite that point of the scale of inches which measures the corresponding tension of vapour. On the left edge of the slider is engraved a scale of equal parts, each of an inch; on the right edge, and having the same zero, is a vernier, applicable to the scale of inches. The lines on these scales are ten times larger than those which the symbols in the dew-point formula represent, but their numerical designations are not changed.

The author has attempted to supply a great desideratum in the practice of marine engineering, by instituting a series of experiments to ascertain what force the waves exert against opposing barriers.

For this purpose he suggests, in some peculiar situations, the use of columns of water or of air, by which the force of each wave can be ascertained; in the one case by the rise of the water-column, or in the other by a pressure-gauge, shewing the same result in atmospheres by compression.

While examining, in polarised light, some of the crystals which he had discovered in Topaz, the author observed certain optical phenomena, depending on a peculiarity of structure. This peculiarity is manifested either in the depolarisation of light, when it gives rise to four quadrants of light, separated by the radii of a black rectangular cross similar to the central portion, or the tints of the first order in the uniaxal system of polarised rings, or in the unequal refraction of common light, which gives rise to the mirage of a luminous point, in the form of concentric circles surrounding the centre of force. In every case there was found a quadrangular cavity in the centre of the intersection of the cross, generally dark and opaque, but in one case having a luminous spot in the centre. These cavities are from the to the of an inch in diameter.

“I take the liberty of addressing you, knowing how much you are interested on the subject of your discovery of the veined structure of glacier ice. I have a specimen (from Mr Stokes's collection) of Mexican obsidian, which, judging from your description, must resemble, to a considerable degree, the zoned ice. It is zoned with quite straight parallel lines, like an agate; and these zones, as far as I can see under the microscope, appear entirely due to the greater or lesser number of excessively minute, flattened air cavities.

When you requested me to give you a memorandum of what appeared to me to be the very glacier-like motion and appearance of Stockholm pitch flowing from a barrel, I considered my observation to have been too casual to be worth writing, and having foreseen that I could arrange an experiment at Gateshead in the beginning of the year, I delayed giving you the memorandum you wished. I had hoped to have been able to inspect and report on my experiment about this time; but I cannot go to Gateshead for some time to come, nor have I had any report of the progress of my pitch glacier since the 6th January, when I was informed it had not moved since the day after I left it, on the 28th December. Your note of yesterday induces me to offer you the following still perfectly vivid impressions of the analogy between ice and Stockholm pitch.

The object of this communication was to shew that, by the use of metallic reflectors for sextants, greater accuracy was obtained in the observed angles, and also that larger angles could be observed. Objects were seen reflected by metallic mirrors, which could not be seen when glass was used; and that when the alloy was formed of pure metals, it was not subject to rust or tarnish, even when exposed to action of the sea air.

The author then exhibited a sextant fitted with these mirrors, which had been employed for a season in the survey of the north coast of Scotland, under Mr Mossman, and read extracts of letters from that gentleman.

The author, after alluding to his former papers on the fluids in topaz, described, in Section I., the form and position of the strata in the minerals in which the cavities occur. They generally occur in immense numbers, occupying extensive strata, and injuring the transparency of the mineral. These strata occupy every possible position, and have every possible curvature; their shape is equally irregular; and it is probable that, in every case, some edge or angle of the stratum touches the surface.

The author, after explaining the methods hitherto proposed for purifying the phosphoric acid of bone earth, and pointing out their inconveniences, mentioned that the chief difficulty was the separation of the magnesia always present in bone earth. The lime, it has been for some time known, may be entirely removed by means of sulphuric acid. In repeating the process of Liebig, which did not succeed in his hands, and which requires the use of alcohol, he found that, after the separation of the lime, there is obtained, by evaporation and heating, a clear and colourless glass, containing all the magnesia: that this glass dissolved completely by boiling in water; but that the solution, if again evaporated and heated to 600° for a quarter of an hour in a platinum capsule, became turbid, and deposited the whole magnesia as an insoluble salt. When water was added, so as to dissolve the phosphoric acid, and the insoluble salt separated by the filter, the filtered liquid was found absolutely free from magnesia, and was a solution of pure phosphoric acid.

Three compartments are pointed out as existing in all rivers, when viewed in connection with the sea, possessing different characteristics, and requiring different classes of works for their improvement. These are, first, The “sea proper,” characterised by the presence of unimpaired tidal phenomena, and including all works connected with the improvement of bars. Second, The “tidal compartment of the river,” characterised by the modified flow of the tide, produced by the inclination of the bed, and embracing works connected with the straightening, widening, or deepening, of the beds of rivers; the formation of new cuts; the erection of walls for the guidance of tidal currents, and the shutting up of subsidiary channels.