net of the electro-magnetic machine, the electricity from the latter melted 8 inches of the same-sized iron wire as was used in the preceding experiment, and a length of 24 inches was made red-hot.

When the electro-magnet of a 5-inch machine was excited by the 2-inch magneto-electric machine, the electricity from the 5-inch electro-magnetic machine melted 15 inches of No. 15 iron wire 0.075 of an inch in diameter.

The author having found that an increase in the dimensions of the machines was accompanied by a proportionate and satisfactory increase of the magnetic and electric forces, a 10-inch electro-magnetic machine was constructed: the weight of its electro-magnet is nearly 3 tons, and the total weight of the machine is about 4 tons. The machine is furnished with two armatures-one for the production of "intensity"-, and the other for the production of "quantity". effects.

The intensity armature is coiled with an insulated conductor consisting of a bundle of thirteen No. 11 copper wires, each 0.125 of an inch in diameter. The coil is 376 feet in length, and weighs 232 lbs.

The quantity armature is enveloped with the folds of an insulated copper-plate conductor 67 feet in length, the weight of which is 344 lbs. These armatures are driven at a uniform velocity of 1500 revolutions per minute, by means of a broad leather belt of the strongest description.

When the direct current from the 13-inch magneto-electric machine, having on its cylinder six permanent magnets, was transmitted through the coils of the electro-magnet of the 5-inch electromagnetic machine, and when the direct current from the latter was simultaneously, and in like manner, transmitted through the coils of the electro-magnet of the 10-inch machine, an amount of magnetic force was developed in the large electro-magnet far exceeding anything which has hitherto been produced, accompanied by the evolution of an amount of dynamic electricity from the quantity armature so enormous as to melt pieces of cylindrical iron rod 15 inches in length, and fully one-quarter of an inch in diameter. With the same arrangement, the electricity from the quantity armature also melted 15 inches of No. 11 copper wire 0·125 of an inch in diameter.

When the intensity armature was placed in the magnet cylinder, the electricity from it melted 7 feet of No. 16 iron wire 0.065 of an inch in diameter, and made a length of 21 feet of the same wire red-hot.

The illuminating power of the electricity from the intensity armature is, as might be expected, of the most splendid description. When an electric lamp, furnished with rods of gas-carbon half an inch square, was placed at the top of a lofty building, the light evolved from it was sufficient to cast the shadows from the flames of the street-lamps a quarter of a mile distant upon the neighbouring walls. When viewed from that distance, the rays proceeding from the reflector have all the rich effulgence of sunshine.

A piece of the ordinary sensitized paper, such as is used for photographic printing, when exposed to the action of the light for twenty seconds, at a distance of 2 feet from the reflector, was darkened to the same degree as was a piece of the same sheet of paper when ex

posed for a period of one minute to the direct rays of the sun, at noon, on a very clear day in the month of March.

The extraordinary calorific and illuminating powers of the 10-inch machine are all the more remarkable from the fact that they have their origin in six small permanent magnets, weighing only 1 lb. each, and only capable, at most, of sustaining collectively a weight of 60 lbs. ; while the electricity from the magneto-electric machine employed in exciting the electro-magnet was of itself incapable of heating to redness the shortest length of iron wire of the smallest size manufactured.

The production of so large an amount of electricity was only obtained (as might have been anticipated by the physicist) by a correspondingly large amount of mechanical force; for it was found that the large electro-magnet could be excited to such a degree that the strong leather belt was scarcely able to drive the machine.

When the electro-magnet of the 10-inch machine was excited by means of the 2-inch magneto-electric machine alone, about twothirds of the maximum amount of power from the 10-inch machine was obtained.

From a consideration of the combined action of the magnetoelectric and electro-magnetic machines, the author points out a remarkable analogy, subsisting between the operation of the static forces of magnetism and of cohesion in modifying dynamical phenomena, which throws additional light upon the nature of the magnetic force.

On reviewing and comparing the whole of the analogous phenomena manifested in the operation of the magnetic and cohesive forces under the varied conditions to which the author invites attention, it appears to him that magnetism is a mode of the force of cohesion, or is, if the term be allowed, polar cohesion acting at sensible distances, the equivalent of magnetic force being obtained at the expense of an equivalent of ordinary cohesive force (in an axial direction) so long as the iron continues to be magnetized.

GEOLOGICAL SOCIETY.

[Continued from vol. xxxi. p. 548.]

May 23, 1866.-Prof. A. C. Ramsay, F.R.S., Vice-President, in the Chair.

The following communications were read :—

1. "Notes on the Geology of Mount Sinai." By the Rev. F. W. Holland.

The physical features of the peninsula were described as exhibiting in the north an extensive tableland of limestone of Cretaceous age, supported and enclosed on the south by a long range of mountains composed of syenite, porphyries, and schistose rocks. Near Jebel Serbal is a mountain of Nummulitic limestone; and a limestone, apparently of more recent date, occurs near Tor and Ras Mohammed. The author further stated that in some parts of the peninsula the syenitic mountains are capped by horizontal beds

their contact with the syenite. This sandstone formed the great mining district of the Egyptians in Sinai, and is now worked for turquoises, which appear to occur more or less in veins. Raised beaches were discovered by the author, on the western side of the peninsula, at elevations of from 20 to 30 feet.

2. "On a new genus of Phyllopodous Crustacea from the Moffat Shales (Lower Silurian), Dumfriesshire." By Henry Woodward, Esq., F.G.S., F.Z.S.

The fossil described consists of the disk-shaped shield, or carapace, of an Apus-like Crustacean, the nearest known form to it being Peltocaris aptychoides, Salter, from which, however, it is at once distinguished by the absence of a dorsal furrow.

A line of suture divides the wedge-shaped rostral portion of the shield from the rest of the carapace, the two parts being seldom found together. From their strong resemblance to Discina, the author proposed for them the generic name Discinocaris, and named the species Browniana, after Mr. D. J. Brown, who first drew his attention to it.

3. On the oldest known British Crab (Protocarcinus longipes, Bell, MS.) from the Forest Marble of Malmesbury, Wilts.' By Henry Woodward, Esq., F.G.S., F.Z.S.

The author stated that three genera and twenty-five species of Brachyurous Crustacea had already been described by Prof. Reuss and II. von Meyer from the Upper White Jura of Germany; but as no limbs or abdominal segments had been met with, it was more doubtful where to place them than the species now described, which had nearly all its limbs in situ, and a portion of the abdomen united. Protocarcinus closely resembles the common spidercrabs (the Maida and Leptopodide) living on our own coasts.

4. "On the species of the genus Eryon, Desm., from the Lias and Oolite of England and Bavaria." By Henry Woodward, Esq., F.G.S., F.Z.S.

The genus Eryon of Desmarest was established for certain extremely broad and flat forms of Astacide found in the Solenhofen limestone near Munich, and first described in 1757. The late Dr. Oppel has recorded fourteen species, two of which, E. Barrovensis and E. (Coleia) antiquus, are from the Lias of England. Mr. Woodward gave descriptions and figures of E. Barrovensis, M'Coy, and five other species, namely, E. crassichelis, E. Wilmcotensis, and E. Brodiei, from the Lower Lias; E. Moorei, from the Upper Lias of Ilminster; and E. Oppeli, from the Lithographic stone of Solenhofen.

5. "Notes relating to the Discovery of Primordial Fossils in the Lingula-flags in the neighbourhood of Tyddynglwadis Silver- leadMine." By J. Plant, Esq., F.G.S.

The discoveries described in this paper included the finding of Paradoxides near the second adit of the Tyddynglwadis mine, in the Lower Lingula-beds, and subsequently of further specimens in the neighbourhood, associated with fragments of Anopolenus and Theca. A detailed examination of the district, undertaken by the author and

Mr. E. Williamson had proved the correctness of their opinion that the strata at Tyddynglwadis belong to the Primordial zone, and that, within a limited area extending east from the boundary line of the Lower Cambrian grits, the rocks ought to yield a series of fossils of Primordial types. This examination had also enabled them to draw a section extending from the junction of the Lower and Upper Cambrians at Cefn Ddiddw to the base of Craig-y-Dinas, which was described in detail by the author, who adopted the following division of the beds :

:

June 6, 1866.-Warington W. Smyth, Esq., M.A., F.R.S.,

President, in the Chair.

The following communications were read :

:

1. "On the Metamorphic and Fossiliferous Rocks of the Co. Galway." By Prof. R. Harkness, F.R.S., F.G.S.

A great portion of the area under consideration was described as being occupied by contorted gneissose rocks, striking east and west, with a prevailing southerly dip towards the granitic area of Galway Bay. Quartzose rocks exhibiting great folds give rise to the bold mountainous scenery of Connemara; and reposing on these, and passing underneath the gneissic strata, is a band of serpentinous limestone, the structure of which is not of animal origin, but results solely from mineral association. The gneissose rocks on the north are covered unconformably by sandstones, the fossils of which indicate the horizon of the Upper Llandovery Rocks. These metamorphic rocks correspond with those of the Highlands of Scotland, representing the Upper Quartz rocks, Upper Limestone, and Upper Gneiss, the positions of which are known in consequence of the Lower Limestones at Durness having been determined to be not lower than the Llandeilo Flags.

2. "On the Metamorphic Lower Silurian Rocks of Carrick, Ayrshire." By J. Geikie, Esq.

In surveying the southern district of Ayrshire, the author and his colleagues recognized the metamorphic character of certain Diorites, Serpentines, and crystalline felspathic rocks independently of each other; and Mr. J. Geikie had also been enabled to trace passages between the various altered rocks, which seemed to him to throw light upon the obscure process of metamorphic action. In this paper he first gave a generalized description of the metamorphic strata, dividing them into four groups-namely (1) Felspathic Rocks, (2) Diorites, (3) Serpentines, and (4) Altered Limestone and Calcareous Greywacke,-and again subdividing the Felspathic rocks into Amygdaloid, Porphyry, Brecciaform rocks, and finely crystalline Felstones, and the Serpentine into Schistose and Com

and stated that the only igneous rocks of the district, consisting of a few dykes of felstone and greenstone, are of much later date than the metamorphism, and have not altered the strata in contact with them. These and other facts described in the paper had enabled him to arrive at the following conclusions:-(1) That the strata owe their metamorphism to hydrothermal action. (2) That the varying mineralogical character of the rocks is due principally to original differences of chemical composition, and not to infiltration of foreign matter at the time of metamorphism. (3) That the highly alkaline portions of the strata have been most susceptible of change. (4) That in beds having the same composition, but exhibiting various degrees of alteration, the intensity of the metamorphism has been in direct proportion to the amount of water present in the strata. (5) That in some places the rocks have been reduced to a pasty condition.

3. "On a Cheirotherian Footprint from the base of the Keuper Sandstone of Daresbury, Cheshire." By W. C. Williamson, Esq., FR.S., Professor of Natural History, Anatomy, and Physiology in Owens College, Manchester.

The specimen in question was discovered by Mr. J. W. Kirkham, in the Lower Keuper Sandstone at Daresbury Quarry. It differs from all footprints hitherto obtained from this district, in being more quadrate, and distinctly that of a scaly animal; the separated toe is also less recurved, and approaches nearer to the other toes. The arrangement of the scales corresponds very closely with that seen in the foot of the living Alligator; many of them run across the foot in oblique lines, as is common amongst living Crocodilians, leaving no room to doubt that they represent true scales, and not irregular tubercles, such as are seen on the skin of some Batrachians. Traces of other impressions of feet occur on the slab, particularly an imperfect one with much larger and more oblong scales, especially under the heel; and this difference is so very similar to what is seen in the fore and hind feet of many Saurians, that Prof. Williamson believed that they did not belong to a Batrachian animal at all, but that they were Saurian, if not Crocodilian, in every feature.

4. "A description of some remarkable 'Heaves' or Throws in Penhalls Mine." By J. W. Pike, Esq.

This mine is situated in the parish of St. Agnes, in Cornwall, and is, from the extraordinary dislocations and heaves of the lodes and veins, without a parallel in any other part of the county. In the immediate neighbourhood of the workings, taking the wellknown law that a lode or vein traversed is older than the one traversing it, there are, in the order of formation, (1) four or five tin lodes, (2) three or four "Downright" lodes, (3) innumerable "gossans, (4) a great number of slides or faults, dipping at various angles, (5) four cross courses, and (6) certain Caunting slides. The mineral productiveness of the tin-lodes is increased by the proximity of the gossans, but not by that of the slides; and although the dislocations are most perplexing to the miner, the district has yielded great riches, and has been worked from time immemorial.