A Phial full of this liquid, one of the first specimens, I believe, that ever made its way to Great Britain, was lately sent to Dr Hooker by Sir Ralph Woodford, Governor of Trinidad. It had been collected in Laguayra by Mr Lockart, Director of the Botanic Garden in Trinidad. Dr Hooker having been good enough to put this rare specimen into my possession, I made a few experiments to determine its constituents. The singular nature of the production, rather than any thing very striking in the results which I obtained, led me to suppose that they would not be unacceptable to the Royal Society.

This curious vegetable production was first made known to the scientific world by M. de Humboldt. But from the very imperfect account which he gives of the Galactodendron utile, there is reason to conclude that he had never seen it. It is certain at least that he had never seen it in blossom. The attention of MM. Boussingault and Mariano de Rivero was drawn to this important liquid by M. de Humboldt. They collected it accordingly, and subjected it to a chemical examination. They found its constituents to be wax, fibrin, sugar, a magnesian salt, which was not an acetate, and water. They could neither detect in it casein nor caoutchouc. The ashes after incineration consisted of a mixture of silica, lime, phosphate of lime, and magnesia.

I have been occupied for about two years past, assisted by the practical pupils in the laboratory belonging to the College of Glasgow, in analysing the most important specimens in my mineral cabinet, which seemed to me to require further elucidation. As my practical pupils are seldom fewer than six, and as they are employed the whole day, from nine in the morning till dinnertime, during the whole year, about six weeks in the summer excepted, which I have been in the habit of spending in the country, the number of analyses which has accumulated within that time, has become so great, and some of the results are so curious, that I have selected a few out of the number, for the gratification of the mineralogical public. It may be requisite to mention, in the first place, that when a pupil comes into my laboratory, the first thing which he does is to transcribe a set of practical rules, which I have drawn up for the benefit of my pupils. He is then set to analyse an easy mineral, with the composition of which I am already acquainted. I either shew him myself the different steps of the analysis, or request some of the farther advanced pupils to superintend the progress of the analysis, and ensure its accuracy.

In the optical and mineralogical classification of crystals which I published in the article Optics in the Edinburgh Encyclopædia, I have arranged Glauberite among those in which I discovered two axes of double refraction. The specimen which I used, however, was so small and imperfect, that I could not measure the inclination of the lines of no polarisation, or ascertain with any accuracy the laws of its action upon light. Mr William Nicol, whose ingenuity is already well known to this Society, put into my hands two specimens of Glauberite, which he had skilfully prepared for showing its system of polarised rings; and, by the use of these, I have been enabled to detect a very remarkable property in this mineral.

1. In the following investigation, it has been my endeavour to elucidate some of the complicated phenomena observable in all the known operations of Magnetic Forces: The labours of so many profound inquirers in this important department of physical science, are indeed such as almost to discourage those less gifted with similar powers of research from engaging in the same pursuit; but knowledge is progressive, and the splendid researches which have displayed the highest efforts of genius serve rather to assist than to deter others in more humble endeavours to promote the advancement of science.

Sir Isaac Newton's theory of the colours of natural bodies, is perhaps the most ingenious and lofty of all his speculations. It was devised, however, at a time when the doctrine of light had made comparatively but little progress, and before the discovery of various principles on which the colours of bodies must depend, or by which, at least, they must be extensively modified. The different dispersive powers of transparent substances;—the irrationality of the spectrum;—the action of striated surfaces;—the decomposition of polarised light;—the reflection of coloured light at the confines of equally refracting media;—and the absorption of common and of polarised rays,—are principles which embrace within their individual range a great variety of facts to which the Newtonian theory of colours bears no relation.

It is nearly a century since chemists began to suspect the nature of the well known mineral usually distinguished by the name of Blende or Pseudo-Galena. Brandt, in 1735, showed that zinc was one of its constituents. In 1744, Funck demonstrated that it was an ore of zinc. Margraaff soon after actually extracted zinc from it. It was impossible to subject it to heat in an open vessel, without perceiving that it contained sulphur. But chemists did not succeed in their attempts to combine zinc and sulphur together. This led them to conclude, that in blende the zinc and sulphur were united together by the intervention of iron.

There being some peculiarities in the construction of the Clock lately set up in this room, which may prove to have considerable influence on the performance of such instruments, and also on their cost and duration, it is presumed that a short notice of them, together with a few preliminary observations, may not be deemed uninteresting to the Society.

An eminent philosopher, in a work recently published, has defined a clock to be “nothing more than a piece of mechanism, for counting the oscillations of a pendulum.” This definition cannot be considered as complete, as besides having to register the oscillations of its pendulum, a clock has to communicate successive impulses to it, to enable it to overcome the friction of its suspension, and the resistance of the air. If a maintaining power were not exerted by the clock, the pendulum would soon be brought to a state of rest.

Notwithstanding the great progress which Mineralogy has made of late years, towards the division of minerals into accurate and well defined species, there are several groups which occur in the oldest mineral systems extant, and which have continued to the present time with very little alteration or improvement. I allude to the minerals classed under the names of Asbestus, Chlorite, and Talc. As these minerals, with the exception of certain varieties of talc, have never been observed in crystals, the important labours of the crystallographer have not been able to throw any light upon them. But, as all mineral species are chemical compounds, and as each species consists of the same constituents united in the same proportions, I thought it not unlikely that an accurate chemical analysis of the different varieties of minerals, at present classed under the names Asbestus, Chlorite, and Talc, would be likely to throw considerable light on their nature, and would inform us whether they constitute peculiar mineral species, or are only varieties of species already well defined and characterized. I propose, in this paper, to give an account of the result of this investigation.

The following observations as to the dentition of the Dugong were made rather more than two years ago, and the inquiry as to the succession and character of the teeth in this interesting animal, and as to the exact composition of its skeleton, was then fully gone into, and all the facts to be now stated proved satisfactorily to myself at least. Notices of these opinions and facts more or less perfect, have been in several ways submitted to the public, both in this country and on the continent; but, as the whole matter was in some measure controversial, tending to call in question the accuracy of a theory as to the dentition of the dugong, promulgated and supported by an anatomist of the highest reputation, I hesitated whether or not the matter to be discussed merited being brought before this Society. Recollecting, however, that the opinions and statements opposed to my own views, had found their way into the pages of a work, of such importance and authority in itself, as to impress readily in the minds of most readers an easy credence as to the exactness of whatever researches there find a place, I hesitated no longer as to the course to be adopted.

The Royal Society of Edinburgh having taken great interest in meteorological observations, it has occurred to me, that the accompanying Meteorological Journals would be acceptable to the Society. I therefore transmit them, in the hope that they may be of some service, in promoting the laudable object of the Society, the science of meteorology.

These journals include a period of twenty-four years, and were kept by the late Mr Pitt of Carlisle, who was long a careful and accurate observer of many atmospherical phenomena. Mr Pitt did not avail himself of the new instruments that are used in meteorology, but understood well the nature and application of those he employed. The thermometer, barometer, and rain-gauge, were the instruments he made use of, and they are probably more important than any other. For many years Mr Pitt had no particular occupation, and meteorology was his hobby. He devoted a great portion of his time to astronomical and meteorological observations, took great delight in keeping his journals, and was scrupulously accurate. From my personal knowledge of his diligence, of his habits of making correct observations, and the systematic fidelity with which he recorded them, I think I can with great safety vouch for the accuracy of the statements contained in his journals.

To the professional zeal and liberality of my lamented friend Dr Adam, late Secretary to the Medical Board at Calcutta, I am indebted for many interesting specimens of the Materia Medica of Hindostan. Among these was a large supply of the powder of the bark of the Mudar or Mudhar, the Calotropis Mudarii of Dr Hamilton, which, with a nearly allied species, had been formerly referred to the genus Asclepias, under the trivial name of gigantea.

The high reputation which the Mudar Powder enjoyed among the natives of India, as a specific for the cure of various cutaneous diseases, induced Mr Playfair, Mr Robinson, and Dr Vos, to investigate its action as a medicine. These gentlemen gave favourable reports of its effects in India, in cutaneous diseases, syphilitic affections, and tape-worm.

1. Anhydrous Silicate of Iron.

This mineral was given me for examination by Patrick Doran, an Irish mineral-dealer, who discovered it in Slavcorrach, one of the Morne Mountains, on the north-east coast of Ireland, forming so conspicuous an object at the southern extremity of the county of Down.

The colour is dark brown, with something of the metallic lustre.

The mineral is foliated, and breaks easily into four-sided prisms, seemingly right; though the summits are very obscure.

The fragments are strongly attracted by the magnet, but they have no poles.

The facts and observations I have now the honour to bring before the Society, were fully made out, and their general correctness ascertained, somewhat more than three years ago. Since that time I have been in the habit of alluding to them, and demonstrating the strictly anatomical part, in my summer course of lectures on comparative anatomy; so that, in short, they may be considered as having, to a certain extent, undergone the ordeal of public opinion. I have thought it right to mention this circumstance, inasmuch as the statements and opinions to be brought forward this evening are contradictory of others which have been promulgated by some anatomists of high standing, and have been received and admitted by naturalists, and by the non-professional, as observations not to be doubted nor controverted; as matters of fact which call for no deeper inquiry; as statements on which unerring doctrinal points might be founded.