The many irregularities to which the vibrations of the horizontal needle are subject, renders the usual method of investigating the terrestrial magnetic intensity, although precise in theory, occasionally uncertain in practice. It has been my endeavour in the following paper, to consider in some measure the most prominent of the causes of these irregularities, with a view of arriving at certain practical deductions, by means of which they may be either greatly palliated, or otherwise avoided.

Although the phenomena of the Pyro-Electricity of Minerals, as it has been termed, and those of the Tourmaline in particular, have, after a long period of neglect, been recently studied by more than one philosopher of eminence, there are a sufficient number of undetermined or debatable points, even at the threshold of the inquiry, to yield facts of novelty and interest to those who will take the trouble to look for them.

Having during the past summer been much engaged in studying the relations of bodies to heat and electricity, I was induced, by having in my possession a considerable number of long tourmalines, to repeat and endeavour to verify some recently published experiments with this mineral. These inquiries brought out several new facts; and, with the hope of adding something to our knowledge in this curious field, I have taken this opportunity of communicating to the Society the results of some very recent experiments.

The country in which Edinburgh is situated has no great elevation above the level of the sea, presenting a gently undulating surface, except where hills of igneous origin, in groups, or perfectly insulated, rise abruptly through the strata, which consist of the sandstones and shales of the coal-formation, with occasional beds of limestone, which they overlie, and this country is more or less covered by old and new alluvial deposits.

The views suggested by these hills to the penetrating genius of Hutton, who may be justly considered the founder of modern geology, first led to the knowledge of the true nature and origin of the trap-rocks. Their analogy to those produced by existing volcanoes, and the phenomena observed in their relations with the secondary strata, leave no doubt as to their having been poured out from the interior of the earth in a fluid or viscid state, through fissures in the strata occasioned by subterranean convulsions—not, however, in the open air, like currents of lava from recent craters, but in sheets or masses at the bottom of the sea, their cooling and consolidation having evidently been slow and gradual, under great pressure, such as might be produced by a large volume of superincumbent water, as was ably illus trated by the experiments of the late Sir James Hall; or by their having been originally formed as dykes, at considerable depths, either below or among the strata.

Some time ago a mineral was put into my hands by Mr Rose, the intelligent mineral dealer of this city, the nature of which was not known, although it had been conjectured to be a variety of Mesotype. Mr Rose obtained it from Count Vargas Bedemar of Copenhagen, who brought it from the Faroe Islands, and subsequently visited this country some years ago. A short chemical examination soon satisfied me that it differed entirely from mesotype; and having ascertained that it contained silica, lime, water, and potash, and no notable quantity of alumina, I was led to conjecture that it would prove to be a variety of apophyllite, although, in that view, it would have presented very remarkable deviations from the ordinary structure of that mineral.

Probably no department of Analytical Mechanics presents greater difficulties than that which treats of the motions of fluids; and hitherto the success of mathematicians therein has been comparatively limited. In the theory of the waves, as presented by MM. Poisson and Cauchy, and in that of sound, their success appears to have been more complete than elsewhere; and if to these investigations we join the researches of Laplace concerning the tides, we shall have the principal important applications hitherto made of the general equations upon which the determination of this kind of motion depends.

The Society has lately been delighted with the discovery of organic remains in our vicinity, which prove, that, at some distant period of unrecorded time, the fertile plains of Mid-Lothian must have furnished food and habitation to beings very different from those which now draw life and enjoyment from their productions. Yet it must be regretted, that, in the conclusions derived from the existence of such remains (with the exception of a few general principles, leading us to regard with deeper feelings of awe and reverence Him who has made all things so wonderfully and fearfully), we have little with which we can sympathise, and still less that can link our existence with that of those of which we see nothing but these imperishable monuments. I confess, however, with the partiality naturally felt by every man for that study to which he may have principally devoted his time and attention, that I regard with far deeper feelings those fleeting sounds—those επεα π˥εζοεν˥α—which, after passing from lip to lip uninjured during the lapse of so many ages, are, when carefully examined, found to have been component parts of those languages, falsely denominated dead, and which can be usefully adduced in illustration of the written records of those mighty spirits who have as yet as far surpassed us in the science of mind, in the purity of their taste, and the perfection of language, as we have surpassed them in the severer sciences—in unfolding the mysterious powers of matter—in discovering the laws according to which they operate—and in subjecting them to the dominion of man. It is with these feelings, and also from a wish to contribute to the great work now so admirably carried on by the German scholars, and by some distinguished fellow-labourers in this country, that of uniting the present and the past, the remote and the near, by proving the consanguinity of the great Caucasian branch of the human family, that the following statement has been drawn up on the force of the Latin particle ve or (as it was written by the more ancient Romans) vae.

Few substances have been made the subject of experimental inquiry more frequently than the compounds of phosphorus and hydrogen, and no subject is so remarkable for the various and conflicting results which it has presented to chemists of the greatest acuteness and practical skill. The obscurity which long hung over the subject has been dispelled, however, in a great measure, by the recent investigations of Henry Rose of Berlin. Although baffled in his early researches, that philosopher returned again and again to the subject, and at last succeeded in determining the chemical functions and true constitution of phosphuretted hydrogen. He has shewn it to be analogous to ammonia in chemical character and composition. But hitherto two compounds of phosphorus and hydrogen had generally been admitted to exist, which were believed to differ in composition, as they do in properties, one being spontaneously inflammable in atmospheric air, and the other not so. Rose establishes beyond all doubt that these gases are essentially of the same composition, and of the same specific gravity; and, indeed, that they are mutually convertible, each into the other, without any addition or subtraction of matter that could be perceived. In explanation of their possessing different properties, under the same composition, allusion is made by Rose to Isomerism, or the doctrine that two bodies may exist identical in composition, but differing in properties. Certainly the existence of two gases, constituted alike, and yet possessing different properties, if established, would afford a firm basis for this doctrine.

There is perhaps no geological problem of greater interest than that by which the conditions of the globe, in respect to the distribution of land and water, at the epoch of the coal formation, might be determined, if the necessary data for its solution could be obtained. We possess sufficient evidence to shew that, since that period, most of the continents and islands of the present day have been elevated above the waters, under which they were originally formed; but such proofs are altogether wanting when we endeavour to restore, in imagination, the probable extent of the older formations that might then have existed as dry land, but which now lie buried in the depths of the ocean, or have since been covered by an accumulation of more recent deposits.

At the close of the preceding session, the Council of the Society did me the honour of entrusting me with the chemical examination of several articles sent not long ago to the Society by Mr Swinton, Secretary to Government at Calcutta. The articles in question are, 1. Specimens of the black varnish used in different parts of Hindostan and the Burmese territories, with specimens of the juices of which these varnishes are said to be compounded; 2. Specimens of naphtha from Persia, and of petroleum from Rangoon; 3. Specimens of wood-oil, a variety of fluid turpentine; 4. Specimens of crude caoutchouc, and of solutions of it in wood-oil.

The only one of these articles which has hitherto yielded results of such interest as to induce me to lay them before the Society, is the petroleum of Rangoon, which appears to contain a compound inflammable principle hitherto unknown.

In the month of August 1830, Reichenbach published his first memoir on the products of the destructive distillation of organic bodies, in which he described a new principle, to which he gave the name of Paraffine, as constantly occurring among those products. Not long after, in 1831, Dr Christison read before this Society a paper, in which he described a substance contained in the petroleum of Rangoon, to which he affixed the name of Petroline. On comparing the properties of these two substances, it was found that they agreed so nearly, that no doubt could be entertained that they were one and the same. As the priority of discovery rests with Dr Reichenbach, the name of Paraffine is now generally adopted. The properties of paraffine are as follows:—It is white, tasteless, inodorous, rather tough, lighter than water, fusible at 125° or 130° F., and it distils unchanged at a higher temperature. It resists the action of the strongest acids and alkalies; and, finally, when pure, it burns with a bright flame without smoke. In a second memoir published by Reichenbach in 1831, he described another of the products of destructive distillation, under the name of Eupione.

The experiments to be detailed in this paper, which chiefly go to establish properties of heat wholly unlooked for, or only suspected to exist, having been made entirely by means of an instrument of great delicacy—the thermo-multiplier of MM. Nobili and Melloni, I shall premise some account of its application to the investigation of some more familiar modes of action.

I propose in this memoir to methedically connect several desultory notices, which I had occasion to read during the last session of the Royal Society's meetings, relative to the Limestones of fresh-water origin in the neighbourhood of Edinburgh, belonging to the carboniferous group of rocks, and to the organic remains which they contain.

Hitherto, the limestones belonging to this older class of deposits have been considered as exclusively of marine origin. I had long since, however, been prepared to expect that a limestone of a fluviatile or fresh-water origin would, some time or other, be proved to exist. For, in judging from analogy, it would be unreasonable to presume, that, when fresh-water limestones appear in the rocks of every later epoch, they should meet with an exclusion in the carboniferous group. In entertaining, therefore, less confined views, I was not at all surprised to find them confirmed in a limestone near Edinburgh, which lately came under my examination,—I allude to that of Burdiehouse. It enclosed none of the marine shells, corallines, or encrinites to be found in the other limestones of the vicinity, but contained in the place of them, and in the greatest possible abundance, the various plants observable in our coal-fields. I also procured from it specimens of fish allied to such as are obtained from beds associated with coal. These facts indicated to me that I had at length found a fresh-water limestone belonging to the carboniferous group of rocks.

It is not my intention to enter into any detailed description of the external characters of the several interesting organic remains which are found imbedded in the limestone of Burdiehouse, that being a task which belongs to their distinguished discoverer Dr Hibbert.

As little do I mean to describe the geological relations of the limestone bed, that being equally the province of Dr Hibbert. It will be sufficient to state generally, that it forms one of the lowest members of the carboniferous group, being inferior in position even to the Encrinal mountain limestone of its immediate vicinity; and that besides its numerous animal remains, some of which will be mentioned in the sequel, it contains throughout its entire mass numerous impressions of land and fresh-water tropical plants.

It may be useful to distinguish some of the functions which water is already admitted to discharge in the constitution of hydrated salts.

Every amphigene ammoniacal salt contains an atom of water, and cannot exist without it. The state of combination of the water is peculiar, and has been represented by supposing that the elements of ammonia unite with the hydrogen of the water, and form a new compound radicle, to which the name Ammonium is given, while the oxygen of the water unites with this radicle, and produces oxide of ammonium. Hence nitrate of ammonia, in which there exist the elements of one atom of nitric acid, of ammonia, and of water, is viewed as anhydrous nitrate of the oxide of ammonium, and corresponds with nitre or the nitrate of the oxide of potassium. But it is not the object of this paper to discuss particularly the state of water in the ammoniacal salts.