Longévité des Arbres, that the general accuracy of calculations is not much affected by such accidents, occasional interruptions to growth being scarcely appreciable in the average of many years. This is possibly true in European trees, and in those of other cold or temperate regions in which the seasons are distinctly marked. In such, the zones are not only separated with tolerable precision, but do not vary much in annual dimensions. But, in many hot countries, the difference between the growing season, and that of rest, if any occur, is so small that the zones are as it were confounded, and the observer finds himself incapable of distinguishing with exactness the formation of one year from that of another. In the wood of Guaiacum, Phlomis fruticosa, Metrosiderus polymorpha, and many other Myrtaceæ, for instance, the zones are extremely indistinct in some Bauhinias, they are formed with great irregularity and in Stauntonia latifolia, some kinds of Ficus, certain species of Aristolochia (as A. labiosa,) and many other plants, they are so confounded that there is not the slightest trace of annual separation. It is also to be remarked that, in Zamias we seldom find more than two or three zones of wood, whatever may be the age of the individual; and yet it appears from Eckton's observations, that a zamia with a trunk only four or five feet high can scarcely be less than 200 or 300 years old.*

:

"With regard to judging of the age of a tree by the inspection of a fragment, the diameter of the stem being known, a little reflection will show that this is to be done with great caution, and that it is liable to excessive error. If, indeed, the zones upon both sides of a tree were always of the same or nearly the same thickness, much error would not perhaps attend such an investigation. But it happens that, from various causes, there is often a great

"According to Decaisne (Comptes Rendus, V. 393,) the zones of wood in Menispermaceæ, each result from the growth of several years."

difference between the growth of the two sides; and consequently that a fragment taken from either side must necessarily lead to the falsest inferences. [Prof. Lindley then gives examples.]—When we hear of the Baobab trees of Senegal being 5150 years old as computed by Adanson; and the Taxodium distichum still more aged, according to the ingenious calculations of Alphonse de Candolle; it is impossible to avoid suspecting that some such error as that just explained has vitiated their conclusions." Introd. to Botany; p. 94-96. Third ed. 1839.

It would be absurdly presumptuous in me to maintain with positiveness any opinion upon a question which thus divides the most profoundly scientific Botanists in the world. I may however acknowledge myself unable to perceive that the suspicion just mentioned is unavoidable. The vast size and structure of the trees referred to would seem likely to protect them completely from atmospheric or any other external causes, by which weakness or material irregularity could be induced, so as to affect the woody deposits on one side of the trunk more than on the opposite. It appears also, from Dr. Lindley's statements, that, though the liability to error may run in either direction, yet that the incompleteness of the data is far more likely to affect the result by bringing out too short a period than one that exceeds the reality.

But, in this age of universal exertion, it must be hoped that some of the many scientific travellers, who are labouring for the service of mankind, will set about the determining of this question, by the best possible examination of the trees, in their places of growth. To saw one through, or to cut it down, manual labour would be ineffectual; and it may be long before the requisite European machinery will be transported into those regions. But it is not too sanguine to expect, that Mr. Bowman's method of taking out cylinders on opposite sides of the

tree, by means of a circular saw like a surgeon's trephine, will be applied; and this will give results so complete that it would be idle scepticism to doubt them.

It should also be observed, that Mr. Bowman, after many observations and experiments, arrived at a general conclusion that M. de Candolle's calculations tended, and would even of necessity operate, to make old trees seem younger than they really are; and consequently, in the cases before us, to bring out a result short of the truth.

[K.]

Referred to at page 222.

UPON DR. YOUNG'S SCRIPTURAL GEOLOGY.

In perusing this book, I have been not a little grieved at the sight which it presents of a pious and amiable man, struggling to give credit and currency to opinions which, to my full conviction, cannot be supported by evidence; but the advocacy of which is likely to mislead some, and to confirm the sceptical prejudices of others. It appears a duty to offer a few observations; but to go over the whole ground which he has opened, would require a treatise of considerable length. Erroneous statements and fallacious arguments can seldom be duly examined, and refuted satisfactorily, without much expenditure of time and labour. I shall select what appear the principal parts of the argu

ment.

A layer of oyster-shells, with the valves separated, and exhibiting other marks of water transport, is found in the Whitby lias, extending for many miles along the coast, and ten or twelve into the interior; and Dr. Y. lays this instance as a principal foundation for the inference of a

diluvial origin to shelly beds generally; and he extends his conclusion to vertebrated animals. (p. 15.) Yet he says not a word upon a fact, of which he seems to have had a glimpse a dozen years ago,* that beds occur of a very peculiar and interesting bivalve, which all confess to be a stranger to the present condition of the seas, Gryphæa incurva, presenting the clearest evidence that the shells had never been drifted, and that the countless individuals lie, as family groups, in their native seats;—and that these beds may be traced, in the same geological position, from Whitby northward to the mouth of the Tees, and southward to the lias of Dorsetshire, and further appearing on the western coasts of Scotland, and again extensively in Germany and in France. If the worthy author could make so much of his seam of disparted oyster-shells, washed over a small piece of land, what ought he not to have concluded from the case of the opposite character, and covering an area a thousand times more extensive?

In like manner, because it is probable that some, or let us say even a large proportion, of the coal-beds, and their sandy and shaly accompaniments have been the results of transportation, he reasons as if all the coal had been formed in this manner. (pp. 10, 14.) But there are eminent geologists, who attribute only the smaller proportion of coal formations to this mode of origin; and conceive that the greater masses have been derived from trees of vast size and close contiguity, submerged in their native seats, without being removed from their place of growth, and marking their scarcely disturbed prostration by the wellknown impressions, on the shale-roofs and bottoms, of their most delicate parts, which would have been greatly defaced or quite obliterated by even a little tossing and drifting.

Geol. Survey of the Yorkshire Coast, p. 242. After briefly describing the species, Dr. Y. says, " Numbers are often found clustering together." This I call a glimpse of the truth. It deserved to have been followed out,

Detached pieces of trunks do indeed occur, whose denuded and broken state suggests a derivation from neighbouring high land, and whose forms and position prove them to have been accidental intruders; but the idea of masses of such vegetation as composes the coal-beds having floated from different quarters, and then, which must have been of necessity, irregularly and confusedly heaped together, appears to be absolutely irreconcilable with the facts exhibited in the impressions of the plants upon the shale, just now mentioned. My kind readers will give themselves pleasure and do justice to the argument, by consulting the specimens of this kind in most of the Museums of Natural History, which happily are multiplied in our country. An excellent suite is in the Adelaide Gallery, presented by my young friend, Mr. Edward Charlesworth, a gentleman whose devotedness to Natural History from his very childhood has produced important results, and promises more. For this purpose, I cannot but also wish that studious attention were given to the accurate and beautiful figures in the Fossil Flora of Great Britain, by Dr. Lindley and Mr. William Hutton; and in Mr. Artis's Antediluvian Phytology."That any considerable part of the plants which formed the beds of coal were drifted at all, appears -to be highly improbable that they should have been brought by equatorial currents from the regions of the tropics, is perfectly chimerical." Fossil Flora, vol. II. Pref. p. xxi. In the same splendid work, an accumulation of facts is brought in proof of this doctrine, and to illustrate the alternations of material in the coal measures, a circumstance on which Dr. Y. lays great stress, (p. 11,) but which those eminent naturalists acccunt for in a way which his objections do not touch. Foss. Flor. vol. III. pp. 28-35. On the other hand, Prof. Phillips deems it "the most probable view, that the plants forming coal were, with the arenaceous and argillaceous substances, swept into the sea

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