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Murchison) are given in his “Synopsis of the Classification of the British Palæozoic Rocks,” 1855. It possesses the weight which must always be recognized as appertaining to the authority of the geologist who, by his own labours, first solved the great problem of the physical structure of the district.

There are other important memoirs of Professor Sedgwick's of which time forbids more than a very passing notice. The memoir “On the Structure of large Mineral Masses,” published in 1831, was the first, and remains to this day the best descriptive paper which has yet appeared on joints, planes of cleavage, nodular concretions, &c.

Always attentive to the purpose of preparing a complete and general classification of the Palæozoic Strata, Professor Sedgwick at an early period in his career printed a memoir “On the Physical Structure of the Older Strata of Devon and Cornwall ;” and another “On the Physical Structure of the Serpentine District of the Lizard.” Of later date are several papers written by him, conjointly with Sir Roderick Murchison, respecting the Devonian System. The principal of these, published in 1840, comprised the work of several previous years, and made known the true nature of the Culm Beds of North Devon, as belonging to the Carboniferous series, and their position in a trough of the subjacent rocks, which rocks, on account of their position and their organic contents, were concluded to belong to the Devonian, or Old Red Sandstone period, a conclusion which was at first controverted, but was ultimately admitted. In another memoir by the same authors in 1828, they conclude that the coarse old red conglomerate along the north-western coast of Scotland and in Caithness is of about the same age as the Old Red Sandstone of South Wales and Herefordshire, and therefore of the Devonian period. They also published in 1840 an account of their general observations on the Palæozoic Formations of Belgium and the Banks of the Rhine, the results of which were considered to harmonize with those derived from other localities. Finally, we may notice another joint memoir. by these authors in 1830, “On the Structure of the Eastern Alps," which, however, had no immediate relation to the researches on the Palæozoic formations.

It will be observed that the memoirs which have been noticed are for the most part pervaded by a certain unity of purpose. The investigations were not on points of merely local interest, but were essential for the elucidation of the geological history of our planet during those early periods of which the records are most difficult to unfold. Few persons perhaps can have an adequate idea of the difficulties he had to contend with when he first entered North Wales as a geologist. Geologically speaking, it was a terra incognita of which he undertook to read the geological history before any one had deciphered the characters in which it is written. Moreover, besides the indistinctness and complexity of the stratification, and the obscurity which then prevailed as to the distinction between planes of stratification and planes of cleavage, there was also the difficulty of what may be called "mountain geometry"—that geometry by which we unite in imagination lines and surfaces observed in one part of a complicated mountain or district with those in another, so as to form a distinct geometrical conception of the arrangement of the intervening masses. This is not an ordinary power; but Mr. Sedgwick's early mathematical education was favourable to the cultivation of it. We think it extremely doubtful whether any other British geologist forty years ago could have undertaken, with a fair chance of success, the great and difficult work which he accomplished.

Such are the direct and legitimate claims of Professor Sedgwick to the honour conferred upon him by the award of the Copley Medal. But there are also other claims, less direct, but which it would be wrong to pass altogether unnoticed. It is not only by written documents that knowledge and a taste for its acquirement are disseminated ; and those who have had the good fortune to attend Professor Sedgwick's lectures, or may have enjoyed social intercourse with him, will testify to the charm and interest he frequently gives to geology by the happy mixture of playful elucidation of the subject with the graver and eloquent exposition of its higher principles and objects.

PROFESSOR SEDGWICK, Accept this Medal, the highest honour which it is in the power of the Royal Society to confer, in testimony of our appreciation of the importance of the researches which have occupied so large a portion of your life, and which have placed you in the foremost rank of those eminent men by whose genius and labours Geology has attained its present high position in our country.

The Council has awarded a Royal Medal to the Reverend Miles Joseph Berkeley for his researches in Cryptogamic Botany, especially in Mycology.

Mr. Berkeley's labours as a cryptogamic botanist for upwards of thirtyfive years, during which they have been more especially devoted to that extensive and most difficult order of plants the Fungi, have rendered him, in the opinion of the botanical members of the Council, by far the most eminent living author in that department. These labours have consisted in large measure of the most arduous and delicate microscopic investigation. Besides papers in various journals on Fungi from all parts of the globe, and in particular an early and admirable memoir on British Fungi, the volume entitled · Introduction to Cryptogamic Botany,' published in 1857, is one which especially deserves to be noticed here. It is a Work which he alone was qualified to write. It is full of sagacious remarks and reasoning; and particular praise is due to the special and conscientious care bestowed on the verification of every part, however minute and difficult, upon which its broad generalizations are founded. Mr. Berkeley's merits are not confined to description or classification ; there are facts of the highest significance, which he has been the first to indicate, and which in many cases he has also proved by observation and by experiments. We refer to his observations on the development of the reproductive bodies of the three orders of Thallogens (Algæ, Lichens, and Fungi), and on the conversion under peculiar conditions of certain forms of their fruit into others ;—to the exact determination of the relations, and sometimes of the absolute specific identity of various forms of Fungi previously referred to different tribes; and to the recognition, in many species and genera, of a diversity of methods of reproduction in giving origin to parallel series of forms. As intimately connected with the life-history of Fungi, the intricate subject of vegetable pathology has been greatly elucidated by him ; and he is indeed the one British authority in this department. His intimate acquaintance with vegetable tissues, and with the effects of external agents, such as climate, soil, exposure, &c., has enabled him to refer many maladies to their source; and to propose methods, which in some cases have proved successful, of averting, checking, and even curing diseases in some of our most valuable crops. In this line of research he has also demonstrated, on the one hand, that many so-called epiphytal and parasitic Fungi are nothing but morbid conditions of the tissues of the plant ; on the other hand, that microscopic Fungi lurk and produce the most disastrous results where their presence had been least suspected.

MR. BERKELEY, I present you with this Medal, in testimony of the high opinion which the Botanical Members of the Council of the Royal Society entertain of your researches in Cryptogamic Botany, especially Mycology; in which latter department your writings entitle you, in their judgment, to be considered as the most eminent living author.

The Council has awarded a Royal Medal to John Peter Gassiot, Esq., for his researches on the Voltaic Battery and Current, and on the Discharge of Electricity through Attenuated Media.

These contributions, most of which are recorded in our Transactions, are of high value, and in some respects peculiar. Their experimental part has been conducted on a scale of magnitude and power unmatched since the days of Davy and of Children, with apparatus of the highest perfection, and with consummate dexterity and skill; and the discussion and interpretation of the facts observed are characterized by sound theory and sober judgment.

It would trespass too much on your time were I to give a detailed account of them, and I shall only select a few which are examples of what Bacon has called “Instantiæ Crucis,” such as, when the mind is undecided between several paths, point out the true one.

1. The first decides a question which was long debated with great vehemence, whether the energy of the Voltaic Battery arises from the contact of its metals, or from chemical action. The first of these opinions was mainly supported by the fact that, when two dissimilar metals are made to

touch, they show signs of opposite electricities when separated. Mr. Gassiot showed, in 1844, that the same occurs when the metals are separated by a thin stratum of air without having been in previous contact.

2. The identity of voltaic with frictional electricity was denied by many, because it gave no spark through an interval of air. Davy had indeed asserted the contrary in his · Elements of Chemical Philosophy, but his statement seems to have been doubted or unheeded. Mr. Gassiot, in the Transactions for 1844, has put the fact beyond dispute; he showed that by increasing the number of cells and carefully insulating them, sparks can be obtained even with the feeblest elements. With 3520 cells, zinc and copper excited with rain-water, he obtained sparks in rapid succession through th of an inch of air ; and a little later added to this a fact of still higher significance, that by exalting the chemical action in the cells, the same or even greater effect could be produced by a much smaller series. The battery of 500 Grove's cells which was constructed for these experiments is probably in some respects the most powerful that was ever made.

3. The currents produced by electric or magnetic induction are of the

is almost daily enriching physical science with precious results. In this new field Mr. Gassiot has been one of the most successful explorers. So early as 1839 he showed that the induction current gives a real spark, and he found that in the flame of a spirit-lamp it could strike at a distance of fths of an inch.

4. The splendid phenomena produced by the discharge of the induction current through rarefied gases or vapours are well known ; in particular the stratification of the light. The cause of this is not yet fully understood, but Mr. Gassiot has made some very important additions to our knowledge of it in the Bakerian Lecture for 1858 and his subsequent communications to the Society. Among these may be named his explanation of the occasionally reversed curvature of the strata, and his discovery of the Reciprocating discharge, which, seeming single, is composed of two, opposite in direction, but detected by the different action of a magnet on each of them, a beautiful test, which is of wide application in such researches. Again, the Torricellian vacuum which he used at first, even when absolutely free from air, contains mercurial vapour : by applying to his tubes a potent freezing mixture, he found that as this vapour condensed, the strata vanished, the light and transmission of electricity decreased, till at a very low temperature both ceased entirely. It follows from this that a perfect vacuum does not conduct-a fact of cosmical importance, which had been surmised before, but not proved; and the desire of verifying this discovery led him to a means of far higher rarefaction. A tube containing a piece of fused hydrate of potassa is filled with dry carbonic acid, exhausted to the limit of the air-pump's power, and sealed; then by heating the potassa, the residual carbonic acid is mostly, or even totally absorbed. Vessels so exhausted, though still containing vapour of potassa, and perhaps of water, have a better vacuum than had been previously obtained, and often cease

to conduct till a little of the alkali is vaporized by heating them, and the gradual progress of the exhaustion gives a wide range of observation.

5. The current of an induction machine is necessarily intermittent, and it has been supposed that the strata are in some way caused by the intermittence, and are possibly connected with the mode of action of the contact breaker. Mr. Gassiot has, however, shown that they are perfectly developed in the discharge of an extended voltaic battery through exhausted tubes. The large water-battery already mentioned shows them in great beauty : the discharge, however, is still intermittent.

6. The same appearance is exhibited by a Grove's battery of 400 wellinsulated cells ; but in this case a new and remarkable phenomenon presents itself. At first the discharge resembles that obtained from the waterbattery, and is like it intermittent; but suddenly it changes its character from intermittent to continuous (so far at least as can be decided by a revolving mirror), and everything indicates that we have now the true voltaic arc. The discharge is now of dazzling brilliancy, and is stratified as before, whence it appears that strata are capable of being produced by the true arc discharge.

7. This change is accompanied by a remarkable alteration in the heating of the two electrodes. Mr. Gassiot had previously shown that, in the ordinary voltaic arc, formed in air of the usual pressure, the positive electrode is that which is the more heated, whilst in the discharge of an induction machine, whether sent through air at the ordinary pressure between electrodes of thin wire, or through an exhausted tube, it is the negative. The discharge through the large Grove's battery, so long as it was intermittent, agreed with the induction discharge in this character as in others, that the negative electrode was that which became heated; but when the discharge suddenly and spontaneously passed from the intermittent to continuous, the previously heated negative electrode became cool, and the positive was intensely heated.

These brief references will suffice to show what a high place Mr. Gassiot holds amongst those who are investigating this new track, which promises such great advance in our knowledge of those molecular forces in the study of which all physical science must ultimately centre. I may be permitted to add, that in his whole career he has sought not his own fame, but the advancement of science ; he has rejoiced as much in the discoveries of others as in his own, and aided them by every appliance in his power. I cannot refrain from mentioning a recent instance in which this liberal and unselfish spirit has been strikingly exhibited. He has had executed a grand spectroscope, furnished with no less than nine faultless prisms, a design in which he has been ably seconded by the skill of the optician Mr. Browning, to whom the construction was entrusted. This magnificent instrument he has placed at the disposal of any Fellow of the Society who may happen to be engaged in researches requiring the use of such powerful apparatus. The instrument is at present at the Kew Observatory, where it is in contemplation to undertake the construction of a highly elaborate map of the spectrum.

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