The minerals of the zeolite family have for many years attracted the especial attention of men of science, and the class has been rapidly extended in proportion to the progress made in its study in a crystallographic as well as chemical point of view. The first characteristic difference, originally observed long since by Cronstedt, and by him considered to be the distinguishing mark of one single mineral species, which he designated Zeolite,—namely, the property of swelling out by heat previous to fusion,—has since been found to belong to a great number of other combinations. These, although materially different from each other in crystallographic form, have proved to be closely allied in chemical constitution, in so far as they consist, without exception, of a silicate of an alkali or alkaline earth, in combination with a silicate of alumina and water. It is evident, then, that the relation of the silicic acid to the base, in both terms, as well as the quantity of water, is capable of considerable variation, so that the general niineralogical formula which should embrace all the members of the zeolite family would be

Where r represents the monatomic alkaline or earthy basis, and the terms u, t, ,T, y, and z, are capable of varying within certain limits.

Although some of the phenomena of Muscæ volitantes may be seen by persons of all ages, and with the best eyes; and though those which are more peculiarly entitled to the name are exceedingly common beyond the middle period of life; yet no account has been given of them that has even the slightest pretension to accuracy. M. De La Hire, in his Differens accidens de la Vue, describes these Muscæ as of two kinds; some permanent and fixed, which he ascribes to small drops of extravasated blood upon the retina; and others, as flying about, and changing their place, even though the eye be fixed. The first kind, he describes as like a dark spot upon a white ground; and the second, as like the knots of a deal board. Some parts of them, he says, are very clear, and surrounded with dark threads, and are accompanied with long fillets of irregular shapes, which are bright in the middle, and terminated on each side by parallel black threads.

It seems extraordinary, that no one should have undertaken a geological survey of Roxburghshire, more especially as the counties to the east and west of it have been examined, and accounts of their formations were published some years ago. It cannot be from its uninteresting character, that the intervening district has been neglected; for it presents as great a variety of apparently distinct formations, as there are in the adjoining counties of Dumfries and Berwick; and some of these have long been the special subjects of speculation and controversy among geologists. The British Association, in the Report of its Meeting held at Cambridge in 1833, propounded the following questions for geological inquiry.

Multiplices Solariorum species, genus testaceorum constituentes, ad Turbinacea Lamarck, ad Gasteropoda Cuvier, pertinens, quæ in geologicis Italiæ stratis reperiuntur, monographico modo investigare fortasse præstat. Ratio nec ambigua; variæ enim dubitandi rationes vigebant, tum circa numerum et nomina specierum, tum circa earundem citationes, et auctorum dissensiones, nec non potissimum circa relationes specierum quæ in Italicis divisionibus supracretaceæ formationis adsunt, sive in se spectatis, sive prout cum viventibus conveniunt aut discrepant.

1. On the 2d September 1839, M. Arago communicated to the Academy of Sciences of Paris a letter by M. Melloni, containing some very interesting experiments on the transmission of Radiant Heat. M. Melloni finds that rock-salt (which is well known to transmit rays of heat from all sources yet tried with equal facility) acquires, by being smoked, the power of transmitting most easily heat of low temperature, or that kind of heat which is stopped in greatest proportion by glass, alum, and (according to M. Melloni) every other substance.

The genus Amphioxus was instituted by Mr Yarrell for the reception of a singular little animal which he received from Mr Couch. The characters of this genus, as given in the History of British Fishes, are, “Body compressed, the surface without scales, both ends pointed; a single dorsal fin extending the whole length of the back; no pectoral, ventral, anal, or caudal fins; mouth on the under part of the head, narrow, elongated, each lateral margin furnished with a row of slender filaments.”

The history of the habits and development of the salmon has been for ages a subject of dispute, even among men of science and experience. The general theory which prevailed regarding its earlier stage of existence was, that the spawn deposited in the autumn or beginning of winter, produced by development the smolts which were seen descending to the sea in the course of the next ensuing spring.

In regard to its after state, some supposed that the smolts which descended the rivers in spring or early summer returned as grilses that same season. Many doubted this theory, and maintained that it was impossible, or very improbable, that they should return so speedily in that greatly enlarged condition; their only argument, however, being founded on the unlikelihood of such a rapid growth.

It has been justly observed that the great discovery of the appropriation of the different portions of the Nervous System to the exercise of different functions, would never have been clearly established, but for the fortunate circumstance that, in certain parts of the body, especially on the face, the nerves of sense and of voluntary motion are distinct throughout their whole course. And this consideration may instruct us that, when we have an organ supplied with a variety of nerves, known to be of perfectly different endowments, the study of the peculiarities of these nerves may give us an insight into the purpose or use of some of those pieces of structure in all parts of the Nervous System, in which we must still admit that we see much contrivance, without understanding its intention.

Since my last communication to the Society on this subject, I have continued my experimental investigation of the proposed law which limited the direct action of the voltaic current to the solvent, in solutions of primary combinations of elementary bodies in the more important solvents. All my farther researches have confirmed the rule in regard to aqueous solutions; and I feel now fully convinced of its truth, although, in the mean time, I have had occasion to see a different view advocated by some other experimenters, to whose opinions I shall afterwards advert. Neither have I seen any grounds for altering my views in regard to alcoholic solutions. In regard to ether, some experiments which I shall afterwards mention, have satisfied me that it would be improper at present to include that solvent in any general rule.

In an experimental inquiry into the action of water on lead, published by me in 1829, in continuation of some previous researches by Guyton-Morveau, it was stated as the general result, that all very pure waters, such as distilled water, rain, and melted snow, act upon lead,—dissolving a trace of it, and causing the formation of an insoluble carbonate of lead in large quantity. It was like-wise shewn, that this action is prevented by the existence of neutral salts in solution; so that most terrestrial waters, as they contain saline matter, act feebly and only in circumstances favourable in other respects. Farther, it appeared to flow from comparative experiments, that this preventive power depends upon the acids of the salts, and not upon their bases;—and that their energy as preventives, that is, the minuteness of the proportion required to annihilate the action, is in the ratio of the insolubility of the compounds which the acids of the salts are capable of forming with oxide of lead.

In analysing Mr Wheatstone's beautiful discovery, that in binocular vision we see all objects of three dimensions by means of two dissimilar pictures on the retina, I trust I have satisfied the Society that the dissimilarity of these two pictures is in no respect the cause of our vivid perception of such objects, but, on the contrary, an unavoidable accompaniment of binocular vision, which renders it less perfect than vision with one eye. On the other hand, it is quite true that, in Mr Wheatstone's experiment of producing the perception of objects of three dimensions by the apparent coalescence of two dissimilar representations of such objects in plano, the dissimilarity of the pictures is necessary in the exhibition of that beautiful phenomenon.

That the eggs of numerous parasitic animals may be deposited in the textures of living beings, and that these develop themselves in such textures, and draw thence their nourishment, has been long known. But that, under particular circumstances, certain cryptogamic plants are capable of germinating and fructifying in the living tissues of animals, and especially in man himself, is a discovery of recent date.

Ever since the discovery by Berzelius of crenic acid in the iron ochre of the water of Porla, in Sweden, chemists have admitted the usual presence of that acid in mineral waters, or those springs containing notable quantities of dissolved inorganic constituents. In such natural waters, also, as are visibly coloured, organic matter is usually understood to be present. Any ideas, however, which may have been entertained respecting the occurrence of organic matter in the perfectly colourless, transparent, and comparatively pure water of ordinary springs, wells, and rivers, have been merely vague and conjectural.

In 1836, I communicated to this Society the results of an extensive series of observations on Terrestrial Magnetic Intensity, made with the Hansteen Apparatus, which is the property of the Society. Some results with a small Dipping Needle, belonging to myself, were also given, but without great confidence in their accuracy.

I held then, however, the opinion which I still do, and to which the remarkable geometrical researches of Professor Gauss of Göttingen on Terrestrial Magnetism have given additional weight, that the element of horizontal intensity ought to be determined, and its laws of variation, in the first place, ascertained, independent of any other. Even should the deduction of total intensity be the sole ultimate object, I hold that an observer with only portable, and consequently imperfect instruments at his command, would do well to separate completely his investigations as to horizontal intensity from those upon dip, and then, by the skilful grouping of each set, having obtained a law of variation of each element according to the co-ordinates of Latitude and Longitude, the two partial results may be combined into the general one of total intensity , whilst either series may be used to check future observations, or be combined with any single future series in which one of the elements should be better determined.

It was observed by Fahrenheit, that the boiling point of water depends on the height of the barometer, the pressure of the air hindering the conversion of water into steam by a resistance which must be overcome by an increase of heat. Deluc and De Saussure contrived apparatuses for making the observation in the open air, and at great heights, and appear to have contemplated the substitution of the thermometer for the barometer upon occasion. They, as well as Dr Horsley, Sir George Schuckburgh, and Mr Cavendish, seem to have regarded the question as one which concerned the fixity of the point used in graduating thermometers, and its requisite corrections, rather than as applicable to barometric purposes generally.

In certain investigations which I have presented to the Society, relative to the modifications which light undergoes when it meets with a medium more dense than that in which it is travelling, the law of force has been supposed to be that of the inverse square of the distance. On re-examination of this subject, I find that there is no necessity for restricting the computations by the hypothesis of any particular law. The conclusions are perfectly independent of the law, provided one of the equations of reduction, the value of which it is not possible to compute by any known methods of analysis, be admitted as an experimental result. The object of the present Memoir is twofold : 1st, To present the analysis of the general theorem of vibrations at the surface of an interrupted medium in its most simple form; and, 2d, To apply the results to the case of reflection unaccompanied by refraction.

It is well known to those who have paid attention to the progress of Fossil Ichthyology that, until the publication of M. Agassiz, the distinctive characters of the orders, genera, and species of Fossil Fishes were but imperfectly understood. Vague analogies were relied on to connect them with the types of living genera, and the looseness of the received specific characters rendered it difficult for the geologist to determine whether the specimens he collected were previously recognised, or still nondescript. It is obvious that useful characters of fossil species are chiefly to be obtained from those portions of their structure least subject to alteration from decay; and as the exterior scaly envelopes of the primeval fishes are usually the portions best preserved and most easily recognised in their rocky sepulchres, M. Agassiz was naturally led to study these with minute attention. This acute observer speedily discovered that, in the form and connections of the scales, he had a general character which would enable him to connect into very natural groups, species differing from each other in size and form. On this basis he has established his four Orders of Fossil Fishes—the Ganoidei, the Placoidei, the Ctenoidei, and the Cyclodei—divisions named from the appearance of the scales.