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trial comets revolving about the earth in the same manner as the solar comets revolve about the sun. That moving in very eccentric orbits, when in perigee, they pass through the atmosphere, are highly electrified, and consequently become luminous. As they approach their lower apside, their electricity is discharged, the body disappears, and a report is heard. This being admitted, it is not strange that, by the violence of the shock, portions of the meteor should be thrown to the earth, while the main body, not sensibly affected by so small a loss, continues to move on in its orbit, and of course ceases to be luminous. (Amer. Philos. Trans. Vol. 6.) We are aware of the objections to this hypothesis, and that it has been ably discussed by Dr Blagden. But when we consider that it was started before the modern discovery of the four small planets, before the discovery of a comet with a period of only twelve hundred days, of which we gave an account in our last number, and before the discovery of a revolving transparent nebulous substance made by Dr Olbers, and mentioned in this journal for April 1820, we think president Clap's conjecture does him great credit
, and that it required far greater reach of speculation than it would now do.
In the sixth chapter of the work under review, there are many valuable details respecting the analysis of metalliferous compounds, in which the author, as he candidly acknowledges, has availed himself largely of the invaluable analytical labours of Klaproth and others. The correctness of these processes appears to have been, for the most part, “submitted to the test of experimental repetition in the laboratory of the Royal Institution. We find many judicious remarks in regard to the difficulties and fallacies by which the young analyst is too apt to be discouraged, and fully agree with our author, that the practice of submitting substances of known composition to analysis, cannot be too strongly recommended to the chemical student. It makes him acquainted with the mutual actions and habitudes of a number of bodies which experience can alone teach, and gives a dexterity of manipulation and an accuracy in conducting experimental inquiries, of which he will find the value when subsequently in the pursuit of original investigations.
We were not a little surprised to see the blow-pipe of the old form, the application of which is exceedingly difficult to be acquired, recommended for general use. No notice is
taken of the improved instrument of Mr Brooke, which, though not quite so portable as the former, is on every other account to be preferred; nor is there any description of the more powerful apparatus of our ingenious countryman, professor Hare. These omissions of Mr Brande should by all means have been supplied by the American editor.
The seventh chapter on the analysis of mineral waters, is preceded by a plan and description of a portable laboratory, which will be found highly convenient for all the necessary operations in these interesting and important researches. Mr Brande has not adverted to the mode of analysis recommended by the late Dr Murray, 'because', as he observes, I cannot admit the existence of incompatible salts to the extent which his principle requires. The student is referred for a variety of useful details to the works of Drs Marcet and Scudamore; Messrs Phillips and Thenard.
The objects of the eighth chapter are the formation of etable substances and their chemical physiology, the analysis of vegetable products and the properties of their proximate component parts, and the phenomena and products of fermentation. The ninth chapter is devoted to the subject of animal chemistry.
The remainder of the volume is principally geological, and is in fact a reprint of the author's • Outlines of Geology,' published in 1817. An account of the principal chemical characters of minerals is an important part of every treatise on chemistry, but we are disposed to consider the introduction of geological speculations as superfluous. As these sections, however, have been retained by the American editor, we should have been pleased to have seen those additions and
emendations,' which they so evidently require. We have not found a reference to a single locality of American minerals, nor to any of those points in the geological structure of this country, which might, with very little labor, have been added. Such additions would have rendered this part of the work far more interesting and valuable. Professor Brande evidently inclines to the Huttonian hypothesis, in regard to the origin of rocks, but has given an interesting and perspicuous abstract of the opinions of other geologists most entitled to attention. The following is bis description of a set of rocks, which from personal examination, we know bear a great resemblance in structure to some in the vicinity of this
town, and to which we alluded in the number of this journal for October, 1820.
Before we quit the subject of primary rocks, it will be right to mention a district of Britain, which, for grandeur of scenery and geological interest, can, I think, scarcely be surpassed. I allude to the country between the eastern extremity of Lochness and Fort George, and especially to the rocks over which the river Fyers pursues its turbulent and winding course.
These are seen in characteristic grandeur in the neighbourhood of the small inn, called the General's Hut, and the scenery becomes more and more impressive and interesting, until we arrive at the celebrated falls of the river. I should call the rock a granitic breccia, or conglomerate ; it appears made up of numerous angular,' and we beg leave to add, rounded. fragments of granitic materials, held together by a silicious cement, and the aggregate is of extreme hardness and durability; masses resembling jasper and agate may also be observed in it.
The general features and rugged irregularities of this district, continues Mr Brande,
• Considered conjointly with the peculiar texture and composition of the materials that form it, present many objects worthy the attention of some geologist, and may be regarded as recording some great natural convulsion, which has not only broken up and reunited certain primary rocks, but has again disturbed their tranquillity, and thrown them into the stupendous confusion they now exhibit.'
The geological part of Mr Brande's work is embellished with a number of engravings, the principal part of which are reduced copies of the admirable sketches of Dr Maculloch, in the Transactions of the Geological Society of London.
Mr Brande takes but a brief notice of volcanoes, and considers that, from the discoveries of sir H. Davy, we may deduce a very adequate solution of the problem of volcanoes, for we have only to suppose the access of water to large masses of those peculiar metals which constitute the alcaline and earthy bases, and we are possessed of all that is wanted to produce the tremendous effects of earthquakes and volcanoes; for what power can resist the expansive force of steam, and the sudden evolution of gaseous Auids, accompanied by torrents of the earths in igneous fusion, which such a concurrence of circumstances would give rise to, and which are the actual concomitants of volcanic eruptions?”
New Series, No. 10. 48
Upon the analysis and composition of soils, Mr Brande has extracted largely from sir H. Davy's Elements of agricultural chemistry. This is a subject of great importance to the practical agriculturist, and is, we are happy to observe, attracting the attention of gentlemen in this country. An examination of the geological structure of any district of country, will be found of essential advantage in promoting the most efficient methods of culture. In illustration of this remark we refer our readers to a valuable paper of Dr Paris, in the 1st Vol. of the Trans. of the Geolog. Soc. of Cornwall. • The line of junction, observes Dr Paris, between the granite and slate formations, may, in many parts, be traced by the eye alone, through tracts of cultivation, from the remarkable fertility which attends it. It may be defined a zone of fertility.' 'Mr Worgan in his view of the agriculture of Cornwall has also noticed a district of great fertility, at the junction of granite and slate. Again, Dr Paris tells us that he was requested by a friend to examine whether any geological arrangements could explain the cause of a particular line in his estate, being more fertile than the neighbouring lands ; upon tracing the direction of the granite and
slate formations, we soon discovered that this line of superior fertility was superincumbent upon the junction of these rocks.' During the summer of 1816 in a geological excursion around the peninsula of the Lizard, Dr Paris was accompanied by a very intelligent farmer of that district, who informed him that the killas (or clay slate) and growan* lands as they came together were much improved in quality, and that they were mutually increased as much as one third in value ; he also stated that the crops upon this "rich vein” were much earlier.'
Art. XXI.—A geological and agricultural survey of Rens
selaer county in the state of New York. Taken under the direction of the honorable Stephen Van Rensselaer. Albany, 1822. pp. 70. The importance of geological and agricultural surveys, at which we have hinted in the preceding article, is beginning to be duly estimated in this country, and a most praiseworthy example has been given by Mr Van Rensselaer of New York,
* The provincial name for decomposed granite.
under whose patronage, an undertaking of this kind has just been completed by Mr Amos Eaton. Mr Eaton's labors we have had occasion to notice in a former number of this journal (Oct. 1820,) and we are happy to find, that the ardor, of which we then expressed our approbation, has not been repressed by the 'impudence of ephemeral reviewers.' The objects to which the liberal patron of Mr Eaton appears to have directed his attention, have, we doubt not, been fully attained, as far as regards collecting materials for a kind of agricultural calendar, to direct the young and inexperienced farmer in regard to times of sowing, planting, &c. &c.' In this laborious undertaking, Mr Eaton tells us, he did not converse with every farmer in the county,' but called on one, at least, in every neighbourhood in all the towns, and wrote down in his presence, the methods of culture adopted by himself, and by his neighbours, as far as had come to his knowledge. This method was evidently well calculated to collect a mass of valuable information, and to throw much light on the state of agriculture in the county. The result of these communications is given in a plain and familiar style.
The remarks of Dr Paris, to which we have alluded in the preceding article, would appear to hold good in respect to some parts of Rensselaer county. At page 23, Mr Eaton observes, that almost every farmer, whose land is situated on slate hills, has observed that his soils are yearly becoming deeper and better,' and that' ten or twelve years ago several fields were chiefly made up of bare rocky (slaty) knolls. Now most of these knolls have become good arable land.'
Mr Eaton describes all the mountainous parts of this county as 'excellent for oats, barley, flax, potatoes, turnips, beets, and carrots. And every part of the county is very productive of either grass or clover.'' He considers the soil of the Knickerbacker estate in Schaghticoke (is there no article in the amended constitution of New York, which gives the legislature the power to change names ?) as the standard of excellence. It contains an average of fifteen per cent of animal and vegetable matter, and a large proportion of carbonate of lime.'
• The rotation method which has always been adopted by this family (they have occupied it one hundred and twenty years, and five generations have been born upon it) has been in the following simple order. Certain fields have been alternately devoted to