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rock. The ascent from the S. E. is by a series of steps formed by the outgoings of the strata.

To the west of this position, the plains are still covered with a deep soil, through which protrude hills and hill ranges, many of them exhibiting a bold and craggy outline. The predominating rocks are different modifications of quartz-rock, many of which are ferruginous. These belong to the clayslate series.

This series appears to be continued on towards Delhi. The celebrated hills of Governdhun, near Bindrabund, is in the line of direction, and is composed of a quartz-rock, which occurs abundantly to the westward of Bhurtpoor. It is characterized by enormous cracks and fissures, which often divide the mass into huge apparently detached blocks; the hills, in many instances, appearing to consist of a series of such blocks, piled the one on the other.

Near the city of Biana, which lies about fifty miles W.S. W. from Agra, there occurs a series of alternations, of a ferruginous quartz rock, with a peculiar conglomerate, containing imbedded agates, agate jaspers, and similar minerals, with adularia, &c. The cementing medium is exceedingly hard and compact, and is itself of the nature of agate. These rocks occupy the rugged termination of a hill-range, which stretches from this point in the direction of Ajimeer. The strata, which are much distorted, are arranged in a similar manner to the older sandstones of Futtypoor Sickree, and probably form the inferior beds of the formation to which the latter belong. The Biana rocks may probably be continued on into the Gewalior country, at least agates, jaspers, and quartzose conglomerates, would appear to be exceedingly abundant in that district. As surface rocks, they occupy but a small space in the Bhurtpore country.

I have been told that copper mines were at one time worked somewhere in the belt of transition rocks which flanks the Bhurtpore district, the exact locality I am not acquainted with. Iron, too, is of abundant occurrence in this belt, and might perhaps be manufactured with advantage.

From the above description it appears that the Bhurtpore district is situated, geologically speaking, to the eastward of the Jeypoor branch of the great primary formation of Rajpootana; and that it is separated from this branch by a belt of transition

rocks*. The newer sandstone of this district would also appear to belong to a great series of rock formations, which has been traced through a large portion of Hindustan, and which forms, with but little interruption, the southern and northern barriers of the valley of the Ganges and Jumna. This series is probably continued on both to the north and south of the primary branch just alluded to, making, on one side, a sweep into the Punjab, flanking, in its course, the great Himalaya formations, and afterwards following a southerly direction through the districts to the west of the Aravulli mountain plateau, which separates Ajmeer from Marwar; while, on the other side, the same series may be traced into Harowteet, Malwa, and Meywar, where it makes a deflection to the south, and is still seen skirting the primary formations of the latter district, being interposed between them and the overlying trap of Malwa. On the border of Guzerat, too, the same series may be observed; and in this portion of the country, the Meywar sandstones seem to take a sweep eastward, so as to unite with the branch to the west of the Aravulli plateau‡. There is also every reason to suppose that the above series is continued on across the Indus into Persia.

In the above general description are included the limestones, and saliferous sandstones, which in some localities appear as the surface-rocks. Under the former, and perhaps also under the latter, the sandstones of the Gangetic series occur; but the whole, undoubtedly, belong to one grand system of formations, identical with the secondary class. Rocks of the transition series, or argillaceous schist series, would also appear to be very

* I use the word "transition” in compliance with custom, but with no theoretical view. The distinction, in India, between the primary and transition series is, to say the least of it, exceedingly ill defined. I have been in the habit of considering all the rocks of Rajpootana as members of one grand formation, which, for the convenience of description, I have separated into three subordinate series, viz. the granitic series, the micaceous schist series, and the argillaceous schist series.

+ This word, by an error of the press, has uniformly been printed Parvistee in my last communication.

This rapid sketch will, I trust, in some degree fill up a hiatus in my friend Mr Calder's excellent outline of the geology of India. See Transactions of the Physical Class of the Asiatic Society, part first, p. 1.

generally interposed between the newer strata and the rocks of the mica-slate and granitic series of Rajpootana; and future observation may probably discover, in this portion of India, the outcroppings of other strata, which may complete the series between the new and old red sandstones. The latter I have described as occasionally appearing, as surface-rocks, in situations the most remote from each other*.

The supporters of the theory of upheaving agencies will not fail to perceive, in the above arrangement, an argument strongly corroborative of their opinions. The fact alone, that the primary rocks of Rajpootana are skirted, or rather, I may say, isolated, by newer formations, corresponding with each other, even at the greatest distances, is a strong presumptive evidence that the former were elevated, or rather forced through a superjacent formation, the remains of which are still found skirting the primary district, which now occupies a central position in reference to the newer formations. The skirting belts are frequently very narrow, and the above seems to be the simplest way of accounting for the appearances observed.

Strong internal evidence of the truth of this theory may be perceived in the structure of the rocks,—in the position of the strata,—in the relative direction of the hill ranges,—and in the different levels at which the newer rocks exist. To this subject I may at a future period revert, and shall at present content myself with remarking, that, posterior to the formation of the newer limestones and sandstones, the agent concerned in the elevation of the great overlying Malwa trap, must have exerted its enormous energy, and that a cause so energetic must have produced effects far beyond the immediate sphere of its operation. Perhaps, too, we may trace in the distribution of the Rajpootana formations the effects of that tendency in the newer marine deposits, to be ruptured along fracture lines at right angles, or nearly so, to one another. Mr Scrope † has supposed that this cause, slight though it apparently be, may have had a great influence in determining the direction of our mountain ranges ; and, in the instance before us, we have seen the skirting belts of newer rocks, first pursuing a northerly and southerly direction

* See Edinburgh New Philosophical Journal, p. 87, No. 21.

+ See his late work on Volcanoes.

VOL. XIV, NO. XXVII.—JANUARY 1832.

F

in Bhurtpore, subsequently a westerly direction into Meywar, where they are deflected towards the south; again following a westerly direction on the borders of Guzerat, and eventually stretching north on the western side of the Aravulli plateau, where they are perceived to form a continuous series with the rocks which skirt the Rajpootana formations, to the north of Jeypoor and Aymeer.

I am sorry that, in this communication, I have been obliged to leave so much to conjecture. To complete a geological survey, with any degree of minuteness, requires the undivided attention of the observer, and infers the power of travelling in whatever direction may be deemed necessary for the determination of doubtful points. A public servant, who has other avocations, must be satisfied with the few observations which he may be enabled to make in the neighbourhood of the line of route, which his duty compels him to follow.

On the Frontal Sinus. By THOMAS STONE, M. D. (Communicated by the Author.)*

In this memoir I propose communicating to the Society the general results of my observations concerning the mode of formation, average extent, and peculiarities, which characterize the frontal sinuses in the human cranium; and when we consider the influence which their development has over the configuration, not only of the cranial, but also of the facial bones, we shall attach due interest to every investigation into their history. With the existence of these sinuses the older anatomists, at least those who immediately succeeded Galen, were not unacquainted, for they were described by Columbus, and Laurentius points them out as demanding especially the consideration of the operating surgeon. It need scarcely be observed, that Vesalius, Albinus, Paaw, Winslow, Cheselden, Monro, and other distinguished anatomists, have likewise described them: but with reference to their origin, they state only, in general terms, that they arise from the diplöe having, where they exist, become ex

* Read before the Royal Medical Society, March 1831.

hausted between the cranial tables; which, after all, amounts to no more than a bare acknowledgment that such cavities do exist. Sommering, in speculating on their origin, hazards the supposition, that bony substance, or diplöe, is first deposited, and then absorbed for the purpose of leaving these spaces; an explanation which appears somewhat clumsy, and which, at any rate, he did not support by any corroborative testimony. Ackermann has had recourse to a theory which appears to me still more fanciful and untenable: he states, that air being drawn up, in the act of inspiration, through the nasal passages, insinuates itself between the tables of the frontal bone, and, by striking against them, mechanically separates them from each other; which hypothetical explanation is refuted at considerable length, under the article Crâne, in the Dictionnaire des Sciences Medicales. It is remarkable that even Sabatier attaches some importance to this vague surmise ;-but, without proceeding to adduce other theories which have been proposed to explain their origin, and which appear alike unsatisfactory, I may briefly premise, that the one which has been recently propounded by the learned and ingenious Dr Milligan, appears to me sufficiently satisfactory; yet, before explaining how his views are coincident with my observations, I must state, which I shall do briefly, the general results of my inquiries concerning the growth of the head at different periods of life.

It is evident that the most conclusive method of obtaining information on this subject, would be to measure the same head at different successive ages; but this, for obvious reasons, has not been hitherto in my power. To supply this desideratum, therefore, I ascertained the extent of the required dimensions of the head in a great number of subjects of the same age, and then found the average extent of each dimension at that period of life. I then arranged in another class the heads of persons of the same, but of a more advanced age; and, after obtaining the individual, found the average dimensions of these; then, by comparing these averages together, deduced the general amount of these dimensions at the ages chosen, and their average increment between the periods allotted to each class. It appears by this investigation, that, during the first four years of life, the head increases equally in all its directions, i. e. in its longitudinal, trans

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