M. Agassiz had already demonstrated the value of fossil fishes, in marking with precision the age of the rocks in which they are found, showed how ably the Professor had illustrated the different genera and species of fishes in the old red sandstone. Mr M. then passed a warm eulogium on the labours of M. Agassiz, which he characterized as almost unparalleled; and stated that the Professor had just completed a long journey from Neufchatel, by Munich, to be able to procure the illustrations of his last fasciculi, which were now laid upon the table. He congratulated geologists on having the merit of being the first to induce M. Agassiz to visit England, by awarding to him the Wollaston medal; and he still more congratulated the meeting upon the satisfaction they must experience in witnessing the valuable results of the judicious grant of money which had been specially allotted to M. Agassiz at Edinburgh, to enable him to illustrate British fossil ichthyology.

11. Dr Traill read a sketch of the physical geography and geology of Spain, founded on his own observations made during a tour in that country. He confined his remarks chiefly to the province of Andalusia. In this interesting country we have every variety of rock, from the oldest primitive up to the tertiary strata. The mica slate of Andalusia contains many interesting minerals, as iron glance, and lead ore. This last mineral is so abundant, that no less than 35,600 tons were extracted in one year. The primitive rocks are succeeded by secondary limestones, in whose fissures interesting osseous remains occur. These limestones extend to the opposite coasts of Africa. This limestone is followed by new red sandstone, gypsum, and marl, abounding in salt and saline springs. Oolite rocks occur near the ancient town of Cartua; and chalk, with flints, is observed at Labriga. Tertiary limestones also occur, as has been noticed by Colonel Silvertop.

Mr Greenough made some observations on the connection of the Alps and the Pyrenees.

12. Mr Smith of Jordanhill read an account of some fossil trees found in a sandstone quarry near Glasgow, viz. near the aqueduct which carries the Forth and Clyde Canal across the Kelvine river. Arguments derived chiefly from the erect position

of the trunks, were adduced to prove that the trees had in the place where they now occur.

grown

After the adjournment of the Section, some of the members proceeded on a geological expedition to Killiney, where they examined an interesting junction of granite and mica slate.

Friday, 14th August.-13. Mr Whewell offered some very interesting explanations and remarks on various points in physics connected with geology, and more particularly on the permanency of the half-tide level, on terrestrial magnetism, on Fourier's views regarding central heat, and on the opinions lately expressed in Poisson's Treatise on Heat.

14. Mr Hartop described some remarkable faults in the southern division of the West Riding of Yorkshire, and offered to continue his investigations.

15. Mr Murchison and Professor Sedgwick gave a lucid and most interesting account of their views regarding the older rocks of England and Wales, endeavouring to point out their subdivisions, so as to complete the series from the old red sandstone to the oldest slate rocks of Cumberland. Mr Murchison treated of that part of the subject relating to the deposits which occur between the old red sandstone and the slaty rocks of Wales. This group of rocks has been termed by Mr Murchison the Silurian System, and has been studied by him during the last five years in Herefordshire, Shropshire, Radnorshire, Brecknockshire, Monmouthshire, and Caermarthenshire. The detailed results of these important investigations will soon be given to the public in the work by Mr Murchison, which is now in preparation. Professor Sedgwick explained the conclusions he had deduced from his elaborate and extensive examination of the greywacke, or slate series, of the north of England and Wales. Professor Sedgwick divides the old transition series into three groups, viz. the Lower Cumbrian, consisting chiefly of slates, and containing no organic remains; the Middle Cumbrian, composed of slates, conglomerates, and porphyries, and containing fossils; and the Upper Cumbrian, which contains much limestone, is fossiliferous, and approaches the lower beds of Mr Murchison's Silurian System.

Mr Murchison stated, that he had discovered fossi fishes in the old red sandstone of the district which he has lately examined, which Mr Agassiz has declared to be identical with the ichthyolites of Caithness. Mr M. is of opinion that the Silurian system of rocks exists to a very considerable extent in Norway.

Some very interesting observations on the transition series were made by Mr Greenough and Professor Phillips.

Dr Daubeny requested the co-operation of the Section, in furthering his inquiries into the nature and phenomena of mineral waters.

16. Dr Jacob read a notice regarding some fossil madrepores from the Queen's County.

17. Professor Phillips made a communication regarding the occurrence of a tertiary deposit on the coast of the north of England, near Burlington.

18. Professor Sedgwick read a letter from Mr Lyell on the fossils of the Crag.

Monday, 10th August.

SECTION C.-CHEMISTRY AND MINERALOGY.

President.-Dr THOMAS THOMSON.

Vice-Presidents.-Dr DALTON and Dr BARKER.

Secretaries.-Dr AFJOHN and Mr JOHNSTON.

Committee. Mr Davy, Mr Vernon Harcourt, Dr Daubeny, Mr Graham, Mr Connell, Dr R. D. Thomson, Mr Kane, Mr Ferguson, Mr Scanlan, Dr Geoghegan, &c.

The Secretary presented to the Section printed copies of tables, exhibiting at a single view the most important properties of simple and compound bodies, for defraying the expenses of the printing of which L. 10 had been allocated at the last meeting of the Association.

1. A paper was then read by Mr Davy, upon the subject of the corrosion of iron by sea water. The observations had particular reference to the injury sustained by the iron of buoys

subjected to the influence of sea-water in harbours, as at Kingstown; where it was recently found that the rings, upon which the safety and utility of the buoys mainly depend, rapidly corrode and are destroyed. Mr Davy turned his attention to the important object of providing a remedy, and preventing the corrosion of the iron; and although his experiments had only recently been commenced, still he considered it proper to bring the few results he had procured before the Section, for the purpose of exciting further inquiry. He found that zinc applied to iron prevented corrosion. Rings of this metal were cast into forelocks for the purpose of experiment, and were found to obviate the waste to which the iron had previously been subject. According to Sir Humphry Davy, the cause of the corrosion of copper and metals in contact with sea water, is attributable to the access of atmospheric air. He considered that if the air was preserved from coming in contact with the metal, no decomposition would ensue. Mr Davy accordingly found, that copper exposed to the action of sea water, free from the influence of air, was not liable to corrosion, and that the effect was influenced by the depth of water. Specimens of metals were exhibited, which had been subjected to the influence of salt water free from air, and no corrosion had taken place; other pieces of metal which were in contact with sea water, subject to the influence of air, were observed to be much injured. Mr Davy attributed the cause of the phenomenon to an electrical decomposition. He stated further, that he had found zinc to preserve tin-plate, both in fresh and salt water. Some observations were made by members of the Section with regard to the action of sea water upon bar and cast iron. Some attributed the greatest corrosion to the former, others to the latter.

2. Mr Ettrick described an improvement which he had made upon Davy's safety-lamp, for the purpose of obviating accidents which are entirely owing to the carelessness of workmen. The Davy lamp, he stated to be perfect in principle. The workmen are in the habit of enlarging the apertures in the wire gauze, and applying their tobacco pipes in order to obtain a light. The modifications recommended at present were, the introduction of very strong glass, to cover the gauze externally.

The glass is again guarded by strong ribs of iron, so that the lamp may be exposed to considerable shocks without danger of injury. A contrivance was also described by which the air was allowed to enter from below, by means of a gauze tube, but so managed, that the gauze could not be reached by the workmen. Various improvements upon the Davy lamp were noticed by different members. Mr Graham stated, that he had found that when the gauze was steeped in an alkaline solution, the flame was prevented from passing so readily, and corrosion was obviated. He considered the only adequate provision against accident to be the employment of a double gauze cover.

3. Mr Kane read a communication in reference to pyroxylic spirit. The experiments which he had made upon this substance corroborate the opinion of its composition entertained by Dumas and Pelligot, who term it methylene, viz. that it is a compound of an atom of carbydrogen, and 1 atom of water, having for its atomic weight 2.

4. Mr Fox described an experiment which he had made with regard to the effect of melted iron upon the magnet. He found that no action was exerted upon it. Hence this is an argument against the idea of a central fire.

5. A letter was read from Dr Turner, reporting the opinion of the committee appointed at last meeting to take into consideration the adoption of a uniform set of chemical symbols for this country. The opinion of the majority was, that those used on the Continent should be had recourse to. It was strongly recommended that the abbreviations should not be carried further than the dots for oxygen; indeed, it was suggested by some that these should be rejected, as they merely express theory, and, consequently, vary according to the view that is taken of the composition in this country and on the Continent; but it is obvious, that if brevity is not carried any further than this, no bad consequences can follow from a system of notation. Dr Thomas Thomson strongly recommended that the centigrade thermometer should be adopted in this country for scientific purposes, as being infinitely better adapted for such purposes than that of Fahrenheit. His suggestion appeared to coincide exactly with the opinion of the Committee.