While referring the present “form of the ground,” in a large degree, to the several agencies of atmospheric and marine denudation, do not let us ignore the, at least, equally efficacious action of subterranean force. This Professor Jukes appears to me to do, to an extent likely to mislead ordinary readers, naturally influenced by his high authority, in the communication from him published in your last number (Vol. III. p. 232). He there speaks of “the action of internal forces,” as “having no direct effect on the external features of the ground.” In a subsequent sentence, indeed, he makes exception, in a parenthesis, of “volcanic cones and craters,” but seemsto consider these exceptional cases as of trifling moment, and to deny altogether the influence of other internal forces in producing superficial elevations or depressions.

Although volcanic rocks of Permian age have long been known to occur abundantly in Germany, their existence in Britain does not appear to have been recognized up to the present time. Trapdykes, indeed, are far from rare among our Permian strata; there occur likewise many igneous masses penetrating the higher portions of the Carboniferous formation; but the former are evidently later than the Permian period, while the latter may be anterior to it. The history of volcanic action in the British isles, so far as I am aware, embraces as yet no clear evidence of Permian volcanos. In the present communication I propose to fill up this gap by showing that during the formation of the Permian sandstones a series of small but active volcanos was scattered over the south-west of Scotland.

The unsatisfactory condition of palæontological botany arises from the imperfect materials which are obtained from the earth's strata. With the exception of two or three remarkable structures, no histological characters have been found whereby the position of a plant can be determined from an examination of its woody structure; so that silicified or calcified woods, which are far from rare, supply little more information than that they are portions of a vascular cryptogam, a palm, a conifer, or other exogen. Of leaves also it may be said that, while a very few natural families have characteristic forms, yet leaves which are undistinguishable are found belonging to plants widely separated in the vegetable kingdom, so that we have little confidence in determinations made from them; indeed, such determinations must be consideredat the best but as guesses at the truth, and these can seldom go further than the natural order, or, perhaps, the genus towhich the fossil belongs. To manufacture species on no other characters than those obtained from slight variations in the form of the leaf, is a reckless multiplication of names, condemned not only by the botanist, but by every one who has carefully examined the variety in form and venation that exist among the leaves of a single shrub or tree. The organs employedby systematists in the classification of plants are so delicate, and so easily perish, that they are very rare as fossils.Fruits, however, are more abundant, and after the flower they may be held of next value in determining the affinities of aplant. Even the separated seeds of living species, or members of living genera, can be positively determined; but when the affinities are obscure, the more or less imperfect specimens of fossil seeds detached from their fruits are very unsatisfactory materials.

Of the various geological evidences inferring a vast duration of the existing contour and conditions of surface since the latest marine submergence, there is, perhaps, none more striking than the accumulation of great masses of Tufa charged with recent organic remains.