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.

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.

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.

It has been long known that the Prussian blue of commerce contains an admixture, in greater or less quantity, of alumina, sulphate of potash, and common alum, one or all of them being easily detected in every specimen. The sulphate of potash and the alum may be separated by frequent boiling in water, but they are seldom in such quantity as to render this process necessary. The alumina may be removed by digestion in muriatic acid, and the washing consequent upon this mode of treatment will free it from all the soluble impurities.

When the alkalies or earths are digested with Prussian blue, in order to form the common Prussiates, and the yellow solution is evaporated, it almost uniformly happens that after the first or second crop of crystals is separated, there remains a dark brownish-red liquid, which either does not crystallize at all, or gives crystals of the required prussiate of a dirty brown colour, and mixed with a greater or less portion of a red matter, either massive, or in small, red, four-sided needles and prisms. This may be observed in preparing the prussiates of lime or soda by the common process, but has been more frequently taken notice of in forming the cyanide of mercury; because the least colouring matter in this salt is at once perceptible, and because in the preparation of it, a partial loss is of greater consequence. To the presence of a portion of this red salt, particularly in extemporaneous prussiates, I attribute those differences in the colour of the precipitates which they give with the metallic oxides, and which have led some to doubt the accuracy of their indications. The grounds of this opinion will appear in the sequel of the present paper.

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.

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.

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.

When in London in spring last year, Mr Parish had the kindness to show me some specimens which he had just received from his son, Mr Woodbine Parish, his Majesty's Consul-General at Buenos Ayres, among which I was surprised and much pleased to find two masses of native iron, exactly similar to the celebrated Siberian block, made known to the scientific world through the exertions of Pallas, having the same vesicular structure, and containing the same straw-yellow coloured olivine firmly imbedded.

I immediately suggested to Mr Parish the propriety of losing no time in making this discovery known, and thereby secure to his son the merit of bringing it before the public; and in order to do this in the most effectual manner, I advised him to present one of the masses to the Royal Society of London, and the other to the Royal Society of Edinburgh; and it is with pleasure that I now find myself deputed to carry his wishes with respect to this Society into execution, by presenting one of the masses as a donation to this institution in the name of his son.

The fruit in this natural order does not appear to have been well understood by most botanists; and I shall therefore attempt to give a general view of what appears to me to be its structure; and most of the parts are visible in the section which is here given (Plate IX. Fig. 1.) of the beautiful but insipid Indian Melon (Cucumis Melo) called Phuti.

The outer parietes (Fig. 1. a,) when young, are thick, fleshy, and undivided by sutures, with an uniform rind, not separable from the fleshy part. As the fruit ripens, the rind in some cases becomes so thin as to be unable to contain the pulpy matter, and bursts either gradually, as in the melon, or with elasticity as in the Momordica and Elaterium of Tournefort. At other times, the rind hardens either into a thin substance like leather or strong paper, as in the Luffa, or into a strong ligneous covering, as in the Cucurbita leucanthema or gourd. In these cases, it sometimes opens horizontally, by means of an operculum, which falls off and leaves an aperture for the seeds, as in Fig. 2. representing the summit of the Luffa called Picinna in the Hortus Malabaricus.

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.

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.

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.

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.

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.

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 sandstone quarry of Corncockle Muir is situated between the rivers Annan and Kinnel, about a mile and half above their confluence, and not quite three miles from the town of Lochmaben in Dumfriesshire. It is near the top of a low, round-backed hill, which stretches about half a mile in a westerly direction, almost in the line of the rivers. This hill rises out of a valley of irregular surface, terminated, at the distance of some miles, on the north and north-west, by a mountainous range of transition rock; on the south by an arm of the same range; and on the east, at a greater distance, by lower elevations, consisting, according to Professor Jameson, partly of floetz-trap and partly of the independent coal-formation. The valley itself is said by the same authority to be of the independent coal-formation, lying on the transition rock, and contains considerable quantities of sandstone interspersed in various parts, and stretching as far as the bottom of the mountains.

In the month of September last (1822), when becalmed in my cutter in the Kyles of Bute, I accidently landed on the most northerly of the Burnt Isles, a small group that stretches across the Kyle or narrow channel between Bute and Argyleshire.

From the appearance of a ridge nearly covered with turf, I imagined at first that kelp had been formerly burnt here, but on examining it more narrowly I discovered that it was caused by the remains of a vitrified fort.