Dobereiner found among his specimens a mineral marked phosphate of iron, which agreed in its characters with the mineral analysed by Trommodorf. He found it composed of This branch of mineralogy has been for some years past studied with much assiduity in Great Britain, chiefly in consequence of the meritorious exertions of the Geological Society of London, and the Wernerian Society of Edinburgh. We are now pretty well acquainted with the names and position of the different rocks which constitute the surface of our island, some of the central parts of England excepted, where the rocks are so much covered with soil, that it is scarcely possible to examine them. Thus, we do not know whether the syenite which occurs at Mount Sorrel in Leicestershire lies over the rocks of the neighbouring country, or whether it rises through them; though a variety of circumstances render the former supposition the most probable. We are likewise imperfectly acquainted with the structure of Derbyshire. Mr. Farey indeed has published a survey of this county, which I believe is very accurate; but, unluckily, his names are all local, and can convey precise information only to the inhabitants of the county. The proper method of proceeding would have been to have given both the local and mineralogical names of these rocks. Mr. Farey indeed treats scientific names, and the cultivators of mineralogy as a science, with ridicule and contempt: but it is surely unnecessary to observe that one man must make a very sorry figure when he sets himself in opposition to all the world. The names of the rocks employed by scientific mineralogists have been universally adopted, and it is beyond the power of any individual to alter them, or to substitute others in their place. The Emperor Claudius endeavoured to introduce two new letters into the Roman alphabet; but all his authority, absolute as it was, was insufficient to effectuate his purpose; and at present we do not even know what these two letters were. Mr. Smith's geological map of the structure of England and part of Scotland was published last summer. It constitutes a material addition to our own knowledge of the structure of this kingdom. It was the result of twenty years of laborious assiduity. Mr. Smith traced the rocks over the country, and ascertained their similarity by means of the petrifactions which they contain. His opinions are precisely the same as those of Werner; though I am not sure that he is aware of the coincidence, and I have no doubt that they originated with himself. Great Britain furnishes perhaps the finest illustration of the Wernerian theory of the position of rocks any where to be found. It even enables us to make some additions to his series which it probably was out of his power to discover in Germany, because the rocks in that country are too much covered with soil. We are enabled likewise to trace the series of formations farther than Werner could in Germany, where the most recent beds either never existed or have been washed away. The different beds of which Great Britain is composed, viewed on the great scale, dip to the east or south-east; so that by travelling west we come always to older and older formations, till at last in the Scilly islands, Argyleshire, Inverness-shire, and Ross-shire, we come to the oldest rocks of all; those which are called primitive, and contain no petrifactions. The Scilly islands are composed of granite which, according to Mr. Majendie's observations, appears to be stratified. There is likewise a ridge of granite rocks that runs from the Land's End to Dartmoor, in Devonshire. On both sides of this ridge rests clayslate in regular beds. This mineral in Cornwall is called killas, which has been preposterously applied by some to greywacke, a rock, to which it bears no resemblance. The position of the rocks in Inverness-shire, and Argyleshire, has not been fully made out. The task is Herculean, and would require the assiduity and enthusiasm of a Saussure. But the whole country, with a few exceptions, is primitive, and the principal rocks in those parts of it which I have visited are gneiss, mica-slate, clay-slate, and porphyry. Several rocks occur in this district which it is not easy to refer to any known species. Among others, that which constitutes the summit of Ben Nevis. The primitive country in this northern part of the island extends to the east coast in the counties of Bamf and Aberdeen. Further north there occur newer formations. But with this remote part of the island we are but imperfectly acquainted. On the west coast the primitive country extends to the Frith of Clyde, but does not cross it. It appears again in Galloway, the structure of which is likewise imperfectly known. It stops short again at the Solway Frith; but seems to re-appear in Cumberland. But this interesting country has never been examined by any person sufficiently acquainted with the science of rocks, to be able to determine its structure with accuracy. It does not appear that Wales contains any primitive rocks; though this has not been made out in a satisfactory manner. Next to the primitive come a class of rocks; called transition. They contain petrifactions, and are very abundant in Great Britain. I do not know that they have been observed further north than the Frith of Forth. But the basis of the Pentland Hills, at least in some places, is a transition formation. The Lamermuir Hills consist chiefly of greywacke and other transition rocks, and they extend VOL. VII. No I. E across the south of Scotland to Dumfriesshire, constituting most of the mountains in Peebles, Roxburgh, Selkirk, and Dumfries. They appear again in Cumberland, and constitute the greatest part of North Wales. They occur likewise in Devonshire, about Exeter and Plymouth, and constitute the whole of the south of Cornwall, as far west as St. Michael's Mount. These rocks are chiefly greywacke, transition slate, and lime-stone. The last two rocks contain petrifactions, chiefly madrepores, and the lowest sea animals. Univalve shells have likewise been seen in the lime-stone at Plymouth and in Dumfriesshire. Over the transition rocks lies the old red sand-stone, the first of the floetz rocks. It is very abundant in Great Britain. It may be traced from Forfarshire with little interruptions, here and there, as far as Manchester. I believe much further, though I have not myself followed it farther south. Professor Jameson has lately shown, that floetz trap rocks occur in it as a subordinate formation, and that the hill of Kinnoul, the Ochils, and part of the Pentlands, are in reality enormous beds of floetz trap rocks, situated in old red sand-stone. This constitutes an important addition to the Wernerian theory. All the coal-beds in the south of Scotland, and the north of England, lie immediately over the old red sand-stone. Perhaps, all the coal-beds in England are in the same position, though this has not been ascertained. The whole of the rocks that cover the coal-beds, constituting the floetz formation of Werner, have not yet been determined. The difficulty is great, because they are almost entirely covered with soil. But it seems probable, that some of the sand-stone formations in Werner's series are wanting, and there appears to be one lime-stone formation which Werner did not find in Germany. The chalk lies over the floetz formations of Werner. It is confined to the south-east corner of England. It begins in Wiltshire, runs east, and divides into two portions, one of which runs north-east, and terminates at Flamburgh Head, in Yorkshire; the other runs east, and dividing, one portion passes by Farnham and Guilford to Dover, where it forms the cliffs. The other goes along the coast, and terminates at Beachy Head. Over the chalk lie three beds, a bed of sand, the London clay, and the gravel which constitutes the surface in the neighbourhood of London. The London clay abounds in marine petrifactions, but none have ever been observed in the surface gravel. IX. METEOROLOGY. 1. The most important meteorological discovery, which has been made during the year 1815, or indeed for many years, is the explanation of the cause of dew by Dr. Wells, in his Essay on Dew, the first edition of which was published in the month of September, 1814. Dr. Wells has shown that dew very seldom or never falls on cloudy nights; that it is deposited most copiously on those substances which radiate heat best, and upon each according to its radiating power; and that those bodies upon which dew falls are many degrees (from 14° to 20°) colder than the atmosphere. Hence the cause of the deposition of dew is obvious. Heat is radiated from those bodies on which it falls, they become colder than the atmosphere; the aqueous vapour in the air is in consequence condensed and deposited upon them. 2. It is well known that, in islands, neither the cold of winter nor the heat of summer is so violent as on continents in the same latitude, or even situated nearer the equator. The surrounding sea moderates both the winter cold and the summer heat, and makes the temperature approach more nearly to a mean. lf the islands be of small size it it no uncommon thing for the winter to pass, even in high latitudes, without any frost: this is often the case in the Orkney and Shetland Islands to the north of Scotland. Snow seldom falls upon them, and scarcely ever lies for any considerable time; but to balance the mildness of the winter, the summer is much colder than it is upon the continent in the same, or even in much higher latitudes. For example, at Stockholm, nearly in the sixth degree of north latitude, nightingales are seen, which shows us that the summer for some months is warmer than at York; but the winter is so severe that neither the chesnut-tree nor the furze can resist it, though these plants thrive very well in the northern parts of Great Britain. After these remarks the reader will not be surprised that in Iceland there was no frost in the southern part of the island after the beginning of January, 1814. (Annals of Philosophy, vol. vi. p. 395.) 3. The following table exhibits the mean temperature of every month, at Plymouth, Sidmouth, and at Tottenham in the neighbourhood of London, according to the tables, published in the Annals of Philosophy. The fourth and fifth columns show the temperature at Somerset House, and on the Frith of Tay in Scotland. Plymouth. Sidmouth. Tottenham. London, Kinfaun's Castle. From this table it appears that Plymouth was warmer during the year 1814 than either Sidmouth or London. It is generally believed that the summers in the neighbourhood of London are warmer than in any other part of Great Britain. If it be true, as I have been told, that the nightingale is never seen in Devonshire, there can be no doubt that the London summers are warmer than those in Devonshire. One year is not sufficient to form any criterion. That the mean temperature of all the three places is lower than that of London, has been reckoned from the heat of springs. The temperature of London in the fourth column is from the register kept at the apartments of the Royal Society; but as in that register the lowest point to which the thermometer falls during the night is not marked, there can be no doubt that the numbers given as the mean in their tables are too high. The quantity of rain that fell in 1814 at Plymouth, Sidmouth, London, and Tottenham, according to the tables already alluded to, was as follows: 427 inches London Plymouth.... Tottenham .... 20.723 inches 24.44 The great quantity of rain which falls annually at Plymouth, compared with those parts of the island which lie further east, has been long known. The difference between the quantity of rain as estimated at Tottenham by Mr. Luke Howard, and at Somerset House by Mr. Lee, is owing to the different position of the two rain-gauges. Mr. Howard's is not far from the surface of the earth, while that at Somerset House is elevated 64 feet above the surrounding ground. Another rain-gauge at Somerset House, placed 75 feet six inches above the ground, gave only 16.867 inches of rain. At Kinfaun's Castle, 129 feet above the level of the sea, the quantity of rain that fell in 1814 is estimated at only 15.59 inches. In the centre of the garden, 20 feet above the level of the sea, the rain was 2005 inches. On a conical detached hill, elevated 600 feet, the quantity was 33.84 inches. The mean temperature of the year was only 43.394. Kinfaun's Castle lies on the river Tay to the east of Perth, in north latitude 56° 23. I have added the mean monthly temperatures at this place to the preceding table, that they may be compared with the temperature in the south of England. 4. It is remarkable that during each of the years 1813, 1814, 1815, there has been a severe frost in London towards the end of November. In 1813 the thermometer sunk down to 20° in the night; but it was above the freezing point during the day; so that the frost was not so much attended to, and it will not be observed in the register published by the Royal Society. The same observation applies to the frost of 1814; but in 1815, on the 17th, 18th, and 19th, of November, the frost was intense during both day and night, and the thermometer stood as low as 18°. X. PHYSIOLOGY. Five papers on this obscure and difficult science have appeared in the Philosophical Transactions for 1815. |