From time to time it has been asserted, that the function of impregnation of the ova of these fish is performed after the manner of that of the cartilaginous, viz., before exclusion. The instances related in proof are commonly of a vague kind, and such that little credit can be attached to them. Recently a more precise example has been adduced,—how the ova of the trout, taken from the abdomen of the parent fish, and placed in a “running stream” apart, included in a perforated box, in due time were hatched, producing young fish. The particulars of the experiment, and the result, were published in the spring of last year, and in more than one of the provincial papers; and Dr Robertson of Dunkeld was named as the institutor and reporter of the trial.

It is well known to the Society, that a mineral, found in the strata of Torbanehill, not far from Bathgate, in the county of Linlithgow, has lately been the subject of a keen lawsuit. Specimens of this mineral were early in the year put into my hands by the lessee, and sometime afterwards by the proprietor of Torbanehill, for the purpose of obtaining a mineralogical opinion on the nature of the mineral. I stated at the time to both parties, that I would carefully examine it before I could presume to offer a decided opinion. In fact, the mineral was not altogether new to me; for, in the two preceding years, I had received specimens of a mineral from Torbanehill, and from Boghead, which I was unable to refer to any described species; and I was therefore determined to give my opinion with due caution, especially as I understood that large interests were involved in the question.

How convenient soever the wet bulb thermometer and the various organic hygrometers may be for giving indications, by simple inspection, regarding the relative states of dryness and humidity of the atmosphere, it is scarcely possible, in conducting meteorological observations, to dispense altogether with instruments calculated for affording more direct information respecting the amount of aqueous vapour present in the air at any particular time.

The memoir which I have now the honour of presenting to the Society contains part of a continued investigation, of which the first results were published in a paper read, last year, before the Chemical Society of London. The nature of the materials experimented on is such, and the scope of the subject so large, as to afford nothing more to all I have at present brought to light than the name of a bare and partial outline; yet the facts I have now to adduce, of some interest in themselves, will increase that of those already made known, and prove of additional service in aiding to complete that desirable object, a knowledge of the chemical constitution of the natural bases. In the paper alluded to, I shewed that, by the action of iodide of ethyl and of methyl upon morphia and codeine, the two most prominent alkaloids of opium, new salts are produced, in which the basic molecules appear to assimilate by their chemical characters to the hypothetical metal ammonium, or its oxide rather; so that, in the system of Hofmann, these peculiar results of natural, and as yet inimitable agencies, would take rank among the nitryle bases.

In a paper on pyromeconic acid read before this Society, and since published in the Philosophical Magazine for September 1852, I have detailed the preparation and properties of a compound obtained by the substitution of an equivalent of bromine for an equivalent of hydrogen in that acid. Having observed that this substitution was very easily effected, I was induced to attempt the formation of an iodopyromeconic acid, in the hope of adding one to the very few instances in which the direct substitution of iodine for hydrogen has been found possible. For this purpose, I digested pyromeconic acid with tincture of iodine, but no success attended the experiment, the acid remaining entirely unchanged. The failure of this attempt led me to speculate as to its cause, and to contrive a method of producing the required substitution which has proved entirely successful, and has the further advantage of being perfectly general, so that its application will enable chemists to obtain iodine substitution compounds in cases in which they have hitherto failed.

That there must be a medium forming a continuous material communication throughout space to the remotest visible body is a fundamental assumption in the undulatory Theory of Light. Whether or not this medium is (as appears to me most probable) a continuation of our own atmosphere, its existence is a fact that cannot be questioned, when the overwhelming evidence in favour of the undulatory theory is considered; and the investigation of its properties in every possible way becomes an object of the greatest interest. A first question would naturally occur, What is the absolute density of the luminiferous ether in any part of space? I am not aware of any attempt having hitherto been made to answer this question, and the present state of science does not in fact afford sufficient data. It has, however, occurred to me that we may assign an inferior limit to the density of the luminiferous medium in interplanetary space by considering the mechanical value of sunlight as deduced in preceding communications to the Royal Society from Pouillet's data on solar radiation, and Joule's mechanical equivalent of the thermal unit.

The mutual actions and motions of the heavenly bodies have long been regarded as the grandest phenomena of mechanical energy in nature. Their light has been seen, and their heat has been felt, without the slightest suspicion that we had thus a direct perception of mechanical energy at all. Even after it has been shewn that the almost inconceivably minute fraction of the Sun's heat and light reaching the earth is the source of energy from which all the mechanical actions of organic life, and nearly every motion of inorganic nature at its surface, are derived, the energy of this source has been scarcely thought of as a development of mechanical power.

The experiments on the rain-fall in the lake district valleys were commenced in 1844,—the mountain gauges were planted in the spring of 1846,—the hygrometrical observations were instituted at the beginning of the year 1852,—and the entire investigation was brought to a close at the end of the year 1853, when its main objects were considered to have been satisfactorily answered and attained.

The tabular observations and general results of the inquiry up to the close of the year 1850, were communicated to the Royal Society of London in four papers, which are published in the Philosophical Transactions of that body. The fifth and concluding paper (comprising the observations, &c. for the years 1851—53 inclusive) I have now the honour to present to the Royal Society of Edinburgh.

Preliminary §§ 97–101. Fundamental Principles of General Thermo-dynamics recapitulated.

97. Mechanical action may be derived from heat, and heat may be generated by mechanical action, by means of forces either acting between contiguous parts of bodies, or due to electric excitation; but in no other way known, or even conceivable, in the present state of science. Hence Thermo-dynamics falls naturally into two Divisions, of which the subjects are respectively, the relation of heat to the forces acting between contiguous parts of bodies, and the relation of heat to electrical agency. The investigations of the conditions under which thermodynamic effects are produced, in operations of any fluid or fluids, whether gaseous or liquid, or passing from one state to the other, or to or from the solid state, and the establishment of universal relations between the physical properties of all substances in these different states, which have been given in Parts I.-V. of the present series of papers, belong to that first great Division of Thermo-dynamics—to be completed (as is intended for future communications to the Royal Society) by the extension of similar researches to the thermo-elastic properties of solids.

The investigation of which I am now about to give an account, was undertaken with the view of determining whether the structure of the Torbanehill mineral was similar to or unlike that of coal. I was aware that the subject would be brought before a court of law, and that many scientific persons of great eminence had already spent much time in the inquiry. With the understanding, therefore, that my evidence, should it be required, was to be limited to the structure of coal and of the mineral in question, I gave directions to Mr Bryson, the optician, of this city, to make thin sections of attested specimens of various coals and of the mineral, conceiving that a careful examination of them would easily determine the point. It was soon apparent, however, that a far more extended series of researches was necessary than I at first anticipated; but as it was also evident, from the marked structural differences which were observed in the sections, that the investigation would not be destitute of positive results, I determined on pursuing it to a conclusion.

The Society has had its attention of late so much directed to the subject of coal, that some apology, perhaps, is necessary for bringing this substance again under notice. I may premise, however, that in doing so, it is not my intention to revive the disputed question as to Boghead gas-coal, nor to take up the time of the Society with what may be considered as unprofitable discussion. I purpose to bring forward a few facts relative to a coal, concerning which there is no dispute, and which presents some vegetable organisms and products calculated, in my opinion, to throw light on the history of carboniferous deposits. Much of the recent difference of opinion on the question of coal has arisen from the mode in which some histologists have chosen to define it. I trust that the result of all our discussions will be to lead to a fuller examination of coal in all its forms,—to a comparison of specimens, both mineralogically and microscopically, from different localities,—and, finally, to an extended report on the subject in which geologists, chemists, and histologists will combine.

In pursuing the investigation of the crystalline constituents of opium, which formed the subject of a previous communication to this Society, I have succeeded in obtaining from the same mother liquor which formed the raw material of my previous researches, a considerable quantity of papaverine, the base recently detected by Merck, and of meconine, the indifferent crystallizable substance discovered by Couerbe in the year 1830. The former was encountered quite unexpectedly in the precipitate from which narcotine and thebaine were prepared by the process described in the first series of these researches. The latter was only obtained after many fruitless trials, in which I was induced to persevere by the desire of comparing it with the substance discovered by myself among the products of the decomposition of narcotine by nitric acid, and described under the name of opianyl. The composition of that substance, as determined by my analyses, approximates very closely to that of meconine; and though the formula assigned to the former is double that obtained by Couerbe from his analysis of the latter, the sole reason for adopting the higher atomic weight was, that the mode in which opianyl was obtained by the decomposition of narcotine, afforded satisfactory grounds for establishing its true constitution.

In the preceding parts of the investigation of the products obtained by the destructive distillation of animal substances, I have entered fully into the method of treating the raw material, and have shown the existence in it of not less than three different series of bases; one, that of which methylamine is the type; a second, of which picoline is an example; and a third series, not yet further examined, to which the provisional name of pyrol bases has been applied. Besides these, aniline is also met with, but whether as an isolated substance or accompanied by the other members of its series, cannot be determined, as none of them possess sufficiently distinctive reactions to permit their detection in a complex mixture.