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.

The mines of Joachimsthal in Bohemia, have long been celebrated for their riches. They were successfully worked at an early period, and though their produce has been exceedingly fluctuating, yet the mining district, in which they occur, continues one of the most important of that country. They seem to have been particularly lucrative and important while they belonged to the house of the Counts Schlick, and when, in the beginning of the sixteenth century, a larger kind of silver coin was introduced into Germany, it took the name of Joachimsthaler, from the place of its coinage, a name which was afterwards changed into thaler, talaro, and dollar.

These mines are not less remarkable for the variety of the species, and for the beauty of the specimens which they have produced. The ancient collections of minerals at Vienna, the Imperial cabinet, that of Von der Nüll, that of Von Morgenbesser, and others, contain magnificent suites of sulphuret of silver, of red silver, &c. chiefly crystallised. The finest specimens, however, of the red silver, and perhaps the finest that ever were known in the species, were dug up so late as 1817 and 1822. The National Museum at Prague possesses one of them, consisting of a group of crystals several inches long, without having any rock attached to it, and weighing about twelve marks, or upwards of six pounds Avoirdupois, the value of the silver of which is more than L. 16 Sterling.

In the session of 1820–21, I had the honour of communicating to the Royal Society, a description of some remarkable atmospheric refractions observed in the Greenland Sea. Since that period, additional opportunities for observation, under circumstances peculiarly favourable, afforded a great number of other examples of a similar kind, along with some still more singular. Among these, the most extraordinary was the inverted image of a ship, which appeared in the lower part of the atmosphere, so distinctly and beautifully defined, that I could venture to pronounce it to be the representation of my father's ship, as, indeed, it proved to be, though we were then distant from each other about 28 miles, and some leagues beyond the limit of direct vision. But an account of the principal of these extraordinary appearances is already before the puplic, and I merely allude to them, in consequence of their similarity to the refractions I have now to describe, that occurred upon our own coasts.

These phenomena occurred during the last summer about Bridlington Bay, and were seen from my residence at Bridlington Quay.

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.

It has been generally known for several years, that, when the acetic acid formed by the distillation of wood is rectified, there is obtained a transparent spirituous liquor, analogous in many respects to alcohol, though very different in others. This liquid has received the name of pyroxylic spirit. It is manufactured by Messrs Turnbull and Ramsay of Glasgow. I have been in the habit for several years of employing it for combustion in lamps instead of alcohol. It is a good deal cheaper, and raises just as good a heat as alcohol; for I can make the small platinum crucible, which I use for drying the products of analysis, red-hot by means of a pyroxylic spirit lamp in a few minutes.

Pyroxylic spirit is as limpid and colourless as alcohol. Its specific gravity, when well rectified, is 0.812. It has an agreeable smell, not, however, quite free from that of naphtha. Its taste is very disagreeable, owing, I believe, to a small portion of naphtha, or empyreumatic oil, which it holds in solution, and from which we cannot free it by any known process. A set of experiments on pyroxylic spirit by Messrs Macaire and Marcet was published in the Bibliotheque Universelle for October 1823. These gentlemen have described several of its properties, and subjected it to an analysis, from which it appears that, like alcohol, it is composed of hydrogen, carbon and oxygen, though the atomic proportions are different.

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.

In the first volume of my “Attempt to establish the First Principles of Chemistry by Experiment,” p. 442, I give the analysis of the sodium chloride of gold, and find the constituents to be

But I state at the same time, my uncertainty whether the gold in the salt was in the state of a chloride or muriate. This uncertainty raising a doubt, whether the peroxide of gold contained two or three atoms of oxygen, I thought it highly necessary to clear it up. In this paper, I shall state the experiments which I have made with that object in view.

In the year 1811, when I was occupied in drawing up an article on Burning Instruments for the Edinburgh Encyclopædia, my attention was in a particular manner directed to the construction of Large Lenses, and to the different methods by which they could be combined with plane and spherical mirrors, for the purpose of obtaining an intense heat from the concentration of the solar rays. I was thus led to examine the inventions and contrivances which had been previously proposed by others, for accomplishing the same object; and after giving a historical account of them, I proceeded to describe the improvements and constructions which had occurred to myself.

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.

Every mineralogist is conversant with some of the facts relative to the subject of this paper. Some of the observations enumerated, are comparatively new, as the attention of naturalists has been only of late more particularly directed towards these facts. Others, which I have had an opportunity of collecting myself, I trust will not be considered uninteresting, as they tend materially to rectify certain ideas connected with the determination of the mineralogical species, the most important branch of natural-historical research.

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.

The phenomenon referred to has long been known, and popularly exhibited in the case of Glauber's salt, without any adequate explanation. A phial or flask is filled with a boiling saturated solution of sulphate of soda or Glauber's salt, and its mouth immediately stopped by a cork, or a piece of bladder is tied tightly over it, while still hot. The solution, thus protected from the atmosphere, generally cools without crystallizing, although it contains a great excess of salt, and continues entirely liquid for hours and even days. But upon withdrawing the stopper, or puncturing the bladder, and admitting air to the solution, it is immediately resolved into a spongy crystalline mass, with the evolution of much heat. The crystallization was attributed to the pressure of the atmosphere suddenly admitted, till it was shewn that the same phenomenon occurred, when air was admitted to a solution already subject to the atmospheric pressure. Recourse was likewise had to the supposed agency of solid particles floating in the air, and brought by means of it into contact with the solution; or it was supposed that the contact of gaseous molecules themselves might determine crystallization, as well as solid particles. But although the phenomenon has been the subject of much speculation among chemists, it is generally allowed that no satisfactory explanation of it has yet been proposed.

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 mineralogical determination of those species, the chief constituent of which is Manganese, has been for a long time destitute of that precision at which other species had long arrived, whose chemical constitution was better known. Two years ago I published, in a memoir “On the Crystalline Forms and Properties of the Manganese-Ores,” the most accurate information I could then collect, partly from some works on mineralogy, partly from my own observations. In the general descriptions which I propose giving here for the mineralogical illustration of Dr Turner's account of their chemical properties, I have availed myself of the corrections given in the translation of the same paper in Poggendorff's Annals by Professor Gustavus Rose, who has corrected or verified the angles given, and compared them again with nature; so that the statements have gained a considerable accession of authority. I have added the description of that species, which consists of the anhydrous peroxide of manganese, and which, from the difference of its properties from all the rest, whatever may be the mode of its formation, should be considered as a species of its own.

It was originally my intention, in entering on this inquiry, merely to ascertain the composition of the ores, the mineralogical characters of which have been so ably delineated by Mr Haidinger in the preceding paper. I had advanced however but a short way in the investigation, when my progress was arrested by doubts both as to the manner of conducting the analyses, and as to the mode of calculating their results. In this uncertainty I found it necessary to extend my original plan, with the view of supplying by my own researches what appeared to be not sufficiently established by the labours of other chemists. I have accordingly divided the essay into two parts; attempting in the first division to ascertain the atomic weight of manganese, and the composition of the artificial oxides of that metal; and in the second, applying the facts thus established to illustrate the chemical constitution of the native oxides described by Mr Haidinger.

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.

In determining the solubility of salts and other bodies in alcohol, it is desirable to operate with a spirit wholly free from water. But anhydrous or absolute alcohol is formed with difficulty, even by the most improved process—that of Richter. In rectifying alcohol from chloride of calcium, as recommended by Richter, I have never obtained it under the specific gravity 0.798 at the temperature of 60°, by a single distillation; but upon rectifying this product again from new chloride of calcium, I generally succeeded in reducing it to 0.796, which is the specific gravity of the standard alcohol of that chemist. The following experiment illustrates this process.

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.