in or about the 43rd parallel of south latitude; and to the south-east of the Island of Madagascar, a situation extremely convenient for ascertaining its exact position, which he considers as an object of great theoretical as well as practical importance. The reading of a paper was then commenced, entitled, "An Experimental Inquiry into the Cause of the grave and acute Tones of the Human Voice." By John Bishop, Esq. Communicated by P. M. Roget, M.D., Sec. R.S. February 26. The reading of a paper, entitled, "An Experimental Inquiry into the Cause of the grave and acute Tones of the Human Voice." By John Bishop, Esq. Communicated by P. M. Roget, M.D., Secretary to the Royal Society, was resumed and concluded. The author considers all the theories hitherto proposed respecting the functions of the organs of the human voice, as not only unsatisfactory, but as being founded on erroneous views. He shows that the modulation of the tones of the voice is not the result of variations either exclusively in the length or in the tension of the vocal chords, or in the size of the aperture of the glottis, or in the velocity or the temperature imparted to the air in its transit through these passages. He regards the organs of the voice as combining the properties of wind and of stringed musical instruments; and shows, first, that for the production of any musical tone it is necessary that the vocal chords should previously be made mutually to approximate; and, secondly, that the muscular forces acting on the arytenoid cartilages and vocal chords are adequate not only to resist the pressure of the column of air issuing from the lungs, but also to render either the whole or certain portions of the vocal chords susceptible of vibration when traversed by the current of respired air. In proportion as these parts of the vocal chords, thus rendered vibratory, increase in length, the number of their vibrations, performed in a given time, diminishes, and the tone of the sound emitted becomes, in consequence, more grave; and, conversely, the tone is more acute as the vibrating portions of the chord are shorter these phænomena being precisely analogous to those which take place in stringed musical instruments. : The author concludes his paper with some observations on the comparative physiology of the voice; and on the extensive range and superior excellence of this faculty in man. March 5.-A paper was read, entitled, "A new Method of discovering the Equations of Caustics." By G. H. S. Johnson, M.A., Tutor of Queen's College, Oxford. Communicated by the Rev. Baden Powell, M.A., F.R.S. Peculiar difficulty has hitherto attended the determination of the equation of the curve formed by the perpetual intersection of rays, which, diverging from a luminous point, are reflected by a polished surface of a given curvature. Curves of this description have been denominated caustics; and the method usually employed to discover their polar equations, or the relation between the radius vector of any point of the curve and the tangent at that point, is both long and inelegant, and is considered by the author as involving considerable inaccuracy of reasoning. He proposes, therefore, to substitute a new method of investigation, by taking the polar equation of one of the reflected rays, and differentiating this equation with respect to the arbitrary quantities solely which determine its position, and thus obtaining the polar co-ordinates of the point of intersection of two consecutive lines; and finally, by elimination, the equation of the curve in which all such points are found. He is thus led to results remarkable for their simplicity, elegance, and generality: and he gives particular applications of his method, exemplifying the facility with which it effects the solution of problems extremely difficult of management by the ordinary methods hitherto employed. His method is also applicable to the determination of the equations of the evolutes of curves, and to various other problems of a similar nature. A paper was also read, entitled, "Discovery of the Metamorphoses in the second Type of the Cirripedes, viz. the Lepades, completing the Natural History of these singular Animals, and confirming their affinity with the Crustacea." By J. V. Thompson, Esq., F.L.S., Deputy Inspector General of Hospitals. Communicated by Sir James Macgrigor, Bart., M.D., F.R.S. The discoveries made by the author of the remarkable metamorphoses which the animals composing the first family of the Cirripedes, or Balani, undergo in the progress of their developement, and which he has published in the third number of his Zoological Researches (p. 76), are in the present paper, which is intended as a prize Essay for one of the Royal Medals, followed up by the report of his discovery of similar changes exhibited by three species of two other genera of the second tribe of this family, namely, the Lepades. The larvae of this tribe, like those of the Balani, have the external appearance of bivalve Monoculi, furnished with locomotive organs, in the form of three pairs of members, the most anterior of which are simple and the other bifid. The back of the animal is covered by an ample shield, terminating anteriorly in two extended horns, and posteriorly in a single elongated spinous process. Thus they possess considerable powers of locomotion, which, with the assistance of an organ of vision, enable them to seek their future permanent place of residence. The author is led from his researches to the conclusion that the Cirripedes do not constitute, as modern naturalists have considered them, a distinct class of animals, but that they occupy a place intermediate between the Crustacea decapoda, with which the Balani have a marked affinity, and the Crustacea entomostraca, to which the Lepades are allied; and that they have no natural affinity with the Testaceous Mollusca, as was supposed by Linnæus, and all the older systematic writers on Zoology. March 12.-Continuation of a former paper "On the twenty-five feet Zenith Telescope, lately erected at the Royal Observatory;" by John Pond, Esq., F.R.S., Astronomer Royal. For determining the place of any star passing the meridian near the zenith, at the Royal Observatory at Greenwich, three different me.. thods may be employed: first, by means of the mural circles; secondly, by the zenith telescope, used alternately east and west; and lastly, by means of a small subsidiary angle, as described by the author in a former paper. The details of computations made according to each of these three methods are contained in the present paper; from which it appears that they all give results nearly identical; and that, when the observations with the two circles are made with sufficient care, the greatest error to be apprehended does not exceed the quarter of a second. "Remarks towards establishing a Theory of the Dispersion of Light." By the Rev. Baden Powell, M.A., F.R.S., Savilian Professor of Geometry in the University of Oxford. In an abstract of M. Cauchy's Theory of Undulations, published in the London and Edinburgh Journal of Science*, the author of the present paper deduced a formula expressing precisely the relation between the length of a wave and the velocity of its propagation; and showed that this last quantity is, in fact, the same as the reciprocal of the refractive index. The author here examines, by means of this formula, the relation between the index of refraction and the length of the period, or wave, for each definite ray, throughout the whole series of numerical results which we at present possess; and the conclusion to which he arrives from this comparison, for all the substances examined by Frauenhofer, viz. for four kinds of flint glass, three of crown glass, water, solution of potash, and oil of turpentine, is that the refractive indices observed for each of the seven definite rays are related to the length of waves of the same rays, as nearly as possible according to the formula above deduced from Cauchy's theory. For all the media as yet accurately examined, therefore, the theory of undulations, as modified by that distinguished analyst, supplies at once both the law and the explanation of the phænomena of the dispersion of light. March 19.-A paper was read, entitled, "Some Account of the Eruption of Vesuvius, which occurred in the month of August, 1834, extracted from the manuscript notes of the Cavaliere Monticelli, Foreign Associate of the Geological Society, and from other sources; together with a Statement of the Products of the Eruption, and of the Condition of the Volcano subsequently to it." By Charles Daubeny, F.R.S., F.G.S., and Professor of Chemistry in the University of Oxford. It appears, from the information collected by the author, that for a considerable time previously to the late eruption of Vesuvius, stones and scoriæ had been thrown up from the crater, and had accumulated into two conical masses, the largest of which was more than two hundred feet in height. On the night of the 24th of August last, after the flow of considerable currents of lava, a violent concussion took place, followed by the disappearance of both these conical hillocks, which, in the course of a single night, were apparently swallowed up within the cavities of the mountain. Fresh currents of lava continued to flow for several days subsequently, destroying about 180 houses, spreading devastation over a large tract of country, and destroying all the fish in the neighbouring ponds and lakes. After the 29th of August, no further signs of internal commotion were manifested, with the exception of the disengagement of aqueous and aëriform vapours from the * See our present volume, p. 16 et seq. crater, a phænomenon which, in a greateror less degree, is at all times observable. The author descended twice into the interior of the crater, which then presented a comparatively level surface; its sides consisting of strata of loose volcanic sand and rapilli, coated with saline incrustations of common salt, coloured red and yellow by peroxide of iron. The vapours which issued from various parts of the surface, collected and condensed by means of an alembic introduced into the ground, were found to consist principally of steam and muriatic acid, with only a slight trace of sulphureous or sulphuric acids. From a trial with solution of barytes, the author concludes that carbonic acid was also exhaled, but neither nitrogen nor sulphuretted hydrogen appeared to form any part of the gas emitted. The steam issuing from the lava contained both free muriatic acid and also muriate of ammonia, which latter salt could not be detected in the gas from the volcano itself. The author conceives that these volatile principles are entangled in the lava, and are subsequently disengaged. March 26.-" On the Temperature of some Fishes of the Genus Thynnus." By John Davy, M.D., F.R.S., Assistant Inspector of Army Hospitals. The author had occasion to observe, many years ago, that the Bonito (Thynnus pelamys, Cuv.) had a temperature of 99° of Fahr. when the surrounding medium was 80°-5, and that it, therefore, constituted an exception to the generally received rule that fishes are universally coldblooded*. Having found that the gills of the common Thunny of the Mediterranean (Thynnus vulgaris, Cuv.) were supplied with nerves of unusual magnitude, that the heart of this latter fish was very powerful, and that its muscles were of a dark red colour, he was led to conjecture that it might, like the Bonito, be also warm-blooded; and this opinion is corroborated by the testimony of several intelligent fishermen. The author endeavours to extend this analogy to other species of the same family, which, according to the reports of the fishermen of whom he made inquiries, have a high temperature, and in whose internal structure he noticed similar peculiarities as in the Thunny; namely, very large branchial nerves, furnished with ganglia of considerable size. In this respect he considers that in these fishes the branchial system of organs makes an approximation to the respiratory apparatus of the Mammalia, and that it probably contributes to the elevation of temperature, resulting from the more energetic respiration which he supposes to be exercised by these organs. He, however, thinks it not improbable that these fish may possess means of generating heat peculiar to themselves, and of which at present we have no adequate idea. He conceives that the situation of the kidneys, of which a considerable portion is even higher than the stomach, and posterior to the gills, and which are of large size, and well supplied with nerves and blood-vessels, may possibly act a part in the production of an elevated temperature; but, on the whole, he is disposed to ascribe the greatest share of this effect to the superior magnitude of the branchial nerves. * See Mr. Brayley's paper on the Distribution of the Powers of producing Heat and Light among Animals, in our last Number, p. 245. GEOLOGICAL SOCIETY. Feb. 4.-A paper was read, "On certain Coal Tracts in Salop, Worcestershire and North Gloucestershire," by Roderick Impey Murchison, Esq. V.P.G.S. Pursuing the inquiry in descending order, commenced at the last Meeting, the author calls attention to certain undescribed carboniferous districts, the outlines of which he has laid down upon the Ordnance Maps. I. "Shrewsbury or upper Coal-measures with freshwater Limestone." The author takes this opportunity of showing, that the coalmeasures near Shrewsbury, which he formerly described as containing a subordinate band of lacustrine limestone, pass up conformably into the lower member of new red sandstone, and are thus proved to constitute the uppermost portion of the carboniferous series. He has this year discovered this freshwater limestone (with the same minute Planorbis, &c.,) in a thin zone of coal-measures extending from Tasley near Bridgnorth to Coughley near Broseley, where the strata, like those near Shrewsbury, also dip conformably beneath the lower new red sandstone. Mr. Prestwich has ascertained that some of the great beds of coal of the Broseley and Colebrookdale field are worked beneath this limestone. II. Western Coal-field of Salop. The Oswestry coal-field, lying on the western borders of Shropshire, is completely separated from that of Shrewsbury, and is the southern termination of the carboniferous zone, which extends from Flintshire by Ruabon and Chirk. It is of small extent, and little productive, containing only one bed of good coal. The millstone grit, which rises from beneath it on three sides, is remarkable for containing beds of cherty breccia, courses of sandy, encrinital limestone, and in the lower portion strata of thick-bedded, red sandstone, in parts undistinguishable from the new red sandstone. The carboniferous limestone beneath this red sandstone, is exhibited on a very large scale in the fine escarpments of Llanymynech, Porth-y-wain and Treflach. The upper part is somewhat magnesian, and contains few fossils, with thin veins of copper ore; the lower is a fine subcrystalline limestone, in which are found Producta hemisphærica, the large basaltiform Coral, and many other fossils characteristic of the formation. Faults are numerous, and in the principal one running from north by east to south by west, the coal is upcast 180 yards. These dislocations increase as they rise upon the hill sides, and decrease as they range towards the plains of Shropshire. III." Central and Southern Coal-fields of Salop." The author mentions that he has accumulated many new facts respecting the coal-fields of the Clee Hills, since his communications in 1832, the principal of which are, That at the Titterstone Clee, the new works established by Mr. Lewis, have proved the existence of productive coal seams under the Hoar Edge, on the western side of * Geol. Proceedings, vol. i. p. 472. |