Geology. A very valuable work has just been published by Dr M'Culloch, entitled, "A Geological Classification of Rocks, with descriptive Synopses of the Species and Varieties, comprising the Elements of Practical Geology." Upon a fu ture occasion we propose to discuss the merits of this book more at length, and shall therefore confine this notice to a bare sketch of its contents, from which, however, our geological readers will be able to draw some conclusions respecting its interest and importance. We have, indeed, regretted that Dr M'Culloch has so long withheld his practical information on systematic geology, since we perused his work on "The Western Islands of Scotland," a work which displays attainments peculiarly fitting him for the task which he has now undertaken.

After some introductory remarks on the methods of arranging rocks, which have been adopted by different mineralogists, and, on the plan of this arrangement and nomenclature, Dr M'Culloch gives the following general catalogue of rocks, succeeded by some remarks on their order of succession in nature.

APPENDIX I.

Volcanic rocks.

APPENDIX II.

Clay, marl, and sand.
Coal.
Alluvia.

Lignite and peat.

Dr M'Culloch apologizes for the introduction of coal and peat into this list, but

the connection of the former with the strata in which it lies, and the important illustrations of its history afforded by the latter, amply justify their insertion.

With respect to the order of succession of the primary class, the claim of granite to the lowest place is unquestioned, but after it no certainty can be obtained, for the others are all found in its occasional contact, and in uncertain order; to illustrate this fact the author inserts a table, shewing the irregular order of succession in rocks in several parts of Britain.

The 7th, 8th, and 9th chapters relate to the aspect and structure of rocks, and, in the 10th, their composition is discussed, illustrated by a valuable catalogue of their component minerals. Dr M'Culloch then proceeds to what we consider as a highly important part of geological science, though hitherto very unscientifically treated; we mean the transition which so often occurs in rocks, not only between the several varieties of each family, but even between the families themselves, in consequence either of their gradual variation of character, or of the loss of one or more of the ingredients which constitute the distinction. Upon these subjects our author has some excellent remarks; they have generally been slurred over by modern geologists, in consequence of the difficulties in which they involve the theorist; but Dr M'Culloch, who is purely practical, and, strange to say, neither Vulcanist nor Neptunist, gives them their due importance and appropriate description.

The 13th chapter contains a synoptic view of the general characters of the families of rocks included in the arrangement before us. To describe the characters of rocks so as to enable the student to recognise them in mass as well as in hand specimens, is a task of no small difficulty, and one which we do not hesitate to say, Dr M'Culloch has performed in a very superior manner.

On the whole, the science of geology, if so it may be called, is much indebted to Dr M'Culloch. In his various papers in the Geological Transactions, and in his book on

the Western Isles, he has shewn himself an indefatigable collector of facts, and a most observant traveller; in the work before us he appears equally successful as an elementary and systematic writer.-Journal of Science, No. XXI.

Spontaneous Combustions.-The following case of spontaneous combustion has been described by Mr James Gullan of Glasgow. See Edinburgh Philosophical Journal, No. VII. page 219.-Having sold a respectable spirit-dealer a parcel of sample-bottles, I sent them to him packed in an old basket, the bottom of which was much broken. To prevent the bottles from falling through, I put across the bottom of the basket a piece of old packing-sheet, which had lain long about an oil and colour warehouse, and was besmeared with different kinds of vegetable oil. About six or eight weeks after, the gentleman informed me that my oily cloth and basket had almost set his warehouse on fire. The basket and cloth had been thrown behind some spirit casks, pretty much confined from the air, and about mid-day he was alarmed by the smell of fire. Having moved away the casks in the direction where the smoke issued, he saw the basket and cloth in a blaze. This fact may give a useful hint to persons in public works, where galipoli, rapeseed, or linseed oils are used in their manufactures; as it is an established fact, (though not generally known,) that these vegetable oils used in cloths, yarn, or wool, in the process of dyeing, and confined for a time from the open air, are very apt to occasion spontaneous fire.

Turkey in Europe. The greater part of European Turkey is still a sort of terra incognita to us, and the information we possess respecting it is neither definite nor accurate. Much confusion, for instance, has been occasioned by the loose way in which the word Greek is used. Sometimes by a Greek is meant a person speaking the Greek language, and at other times a person belonging to the Greek Church. Hassel, a German statistical writer in great estimation, makes Turkey in Europe, on the best and most recent authorities, to contain a population of nine millions four hundred and eighty-two thousand; of this population the Turks do not amount to one third part, and the Greeks alone amount to about five millions; but then the population professing the Greek religion amounts to a much greater number than five millions. For instance, the Bulgarians, about 1,800,000, a Sclavonic people, are partly of the Greek, and partly of the Mahomedan religion. The Servians, about 960,000, another Sclavonic people, are all of the Greek religion. The Bosnians, about 850,000, are also of the Greek religion. The Albanians speak Sclavonic and

the old Illyrian language, and are partly of the Greek, and partly of the Mahomedan religion. The Wallachians and Moldavians, 1,230,000, according to Hassel, but about one million and a half in num. ber, according to Mr Wilkinson's account, are only Greeks by religion.

Though the Turks form so small a part of the population in Europe, they are very numerous in Asia, where their chief strength has always lain. From Africa, however, they are not likely to derive any assistance at the present moment.

The Northern Expedition.-The following particulars of the expedition towards the North Pole, now on the eve of sailing, may be acceptable:

The Officers of the Fury are Captain Parry, Lieutenants Nias and Reid, Mr Edwards, surgeon, Mr Skeoch, assistantsurgeon, and Mr Hooper, purser; Mr Fisher, astronomer, and Mr Allison, Greenland master. The midshipmen are Messrs Ross, Henderson, Bushnan, and Crowley; Mr Halse, captain's clerk, and a Greenland mate; the whole complement, including officers, being 61. In the Hccla, Captain Lyon, Lieutenants Hopner and Palmer, Mr Alexander Fisher, surgeon, and Mr M'Laren, assistant-surgeon; Mr Jermain, purser, Mr Fyfe, Greenland master; and Messrs Richards, Griffiths, Bird, and Shearer, midshipmen; Mr Mogg, captain's clerk, and a Greenland mate; the whole crew, including officers, being 60. This vessel has no astronomer.

In addition to the preparations which were made for the last voyage to guard against the cold, the vessels are now lined with cork all around the inside, and have also an apparatus by a Mr Sylvester, for conveying heated air all round the lower deck, and a small branch from the main pipe, opening into each of the officers' cabins. They take out no salt beef; but, in lieu of it, a large quantity of beef, veal, and mutton, preserved by Messrs Donkin and Company's process. In other respects, the provisions are the same as in the last expedition, only that there is a larger quan tity, each ship being provided with stores and provisions for three years. They have also more coals, for each vessel takes 115 chalders.

The Nautilus, a hired transport, is to accompany them as far as Davis's Straits, in order to carry out part of their fuel and stores, &c. and it is reported that another vessel is to be sent to Behring's Straits in the course of next year to meet them there, should they proceed in penetrating to the Pacific, with an additional supply of such articles as may be deemed necessary.

The men are to receive three months pay in advance, in order to enable them to furnish themselves with clothes and other necessaries for the voyage.

Captain Parry, in a letter to Dr Rigby of Norwich, dated April 25th, observes, "Every thing belonging to our equipment is as I could wish. I have not a thing left undone, which has suggested itself as useful; and we go out under every circumstance, which, as far as we can judge, is likely to tend to success. You will remember, however, that I am not over sanguine, and you will oblige me much in checking, by every opportunity in your power, the sanguine expectations which are, I believe, too generally formed of our complete success."

Professor Playfair; Naval Tacties. The Transactions of the Royal Society of Edinburgh, Vol. IX. Part I. recently pub fished, contain, among other interesting papers, A Memoir relating to the Naval Tactics of the late John Clerk, Esq. of Eldin, being a fragment of an intended Account of his Life; by the late JOHN PLAYFAIR, Esq. F.R.Ś. Lond. and Edin. (p. 113. 138.)

It is scarcely necessary to inform our readers, that the celebrated manœuvre of breaking the enemy's line, by the practice of which we have so often annihilated the proudest armaments of France and Spain, was the undisputed invention of our countryman, the late John Clerk, Esq. of Eldin, a country gentleman, who had no prac tical acquaintance with naval affairs. Mr Clerk had begun, so early as 1779, to make the principles of his system known to his friends. The manoeuvre was first successfully practised by Lord Rodney in April 1782; and it was by the application of the same principles that Lord Howe, Lord St Vincent, Lord Duncan, and Lord Nelson, achieved their splendid victories.

Mr Playfair had proposed to draw up a biographical account of his friend; but he was prevented by ill health from completing his design. Although the present me. moir, however, is only a fragment, yet it contains a full account of the great invention of Mr Clerk; and is characterised by the usual eloquence and ability of its distinguished author. It will be read therefore with the double interest, which must ever be excited, to a subject so deeply national, and to the last literary production of a philosopher so universally and deservedly

esteemed.

Aerostatics. A paragraph appears in the daily papers, stating, from a Roman Journal, that M. Mignorelli of Bologna has discovered a method of giving horizontal direction to balloons.

Oxford. The picture gallery of the University of Oxford has lately been embellished by models of the Temple of Neptune at Paestum, and of the Amphitheatre at Verona.

Discovery of Coffins.-A few days ago, there were discovered, in the neighbourhood

of Portobello, seven or eight feet below the ground, three stone coffins rudely put to gether, each containing a human skeleton of an ordinary size. The bones were quite entire, though rather brittle; and from their position, it would seem that the bodies to which they belonged had been interred with their legs across. Two of the skulls at the back had been penetrated by some sharp instrument. At the head of each were deposited a number of sharp flints; from which it is conjectured by antiqua ries, that the inhumation had taken place previous to the use of metal being known in this country! Above these coffins was a tumulus of sand, and what is very remarkable, the roots of some shrubs in search of nutriment, had penetrated the coffins and skulls of the skeletons, about which and the ribs they had curiously twisted themselves. The cavities of the skeletons indeed were entirely filled with vegetable matter. These interesting relics of humanity were generously allowed by Mr Miller, the proprietor of the ground, to be transferred to Dr Barclay's valuable museum, where they may now be seen. We take this opportunity of doing justice to the great liberality of Dr Barclay, who readily admits every person of respectable appearance to visit his collection, and even to take drawings of any article.

Walking upon Water.-A Mr Kent of Glasgow has invented a machine, by which he is enabled to walk on the surface of the water with perfect safety, at the rate of three miles in the hour. On Monday morning last, between four and five o'clock, Mr Kent walked on the Monkland Canal at the rate of three miles in the hour, which was witnessed by about 200 persons, who all testified their approbation at the performance.-Glasgow Courier.

The Thermometer.-Fahrenheit's thermometer has risen in three days from 45 to 70 degrees, a difference of temperature equal to that change of temperature, in different latitudes, which might be experienced by as sudden a transition from the north of England to the south of Italy. April 22, at nine A. M. it was at 45 degrees; April 23, at the same hour, at 55 degrees; April 24, at three P. M. the mercury stood at 70 degrees in a north-east aspect in the shade; April 26, at two P. M. the same thermometer was at the extraordinary height of 73 degrees.-Cambridge Chron.

The thermometer in the open air in Barton Street, Westminster, on 25th April, was at 80 degrees.

Astronomical Prize Question.-The Astronomical Society of London have offered their gold medal and twenty guineas, “ For the best paper on the theory of the motions and perturbations of the satellites of Saturn." The investigation to be so con