Page:John Gilbert Baker - The Flora of Warwickshire (review) - 1891 - Nature, London, 43 (1114); 413-314.pdf/1

5, 1891] adapt themselves to the reactions of the mineral, and feeling himself at last in touch with the affinities of the; impenetrable atom. Let such consider and beware.

The description given of the contact-phenomena (p. 480) has at present an especial interest, and the author freely uses the term "schist" for the distinctly foliated rocks which are common along the flanks of the great chain, although such recks are undoubtedly of Ordovician age. This is mere justice to the structures developed, and an encouragement to petrologists in the field, who are apt to resent a terminology based in any way upon geological age. While Prof. Sollas points out how the foliation in this case preceded the intrusion of the granite, we may take it that the same earth-movements produced both the one and the other at no long interval, the foliation being a prelude to the final yielding of the uptilted rocks.

The phenomena of foliation in the schists, and of flowstructure in the granite, may be studied by any visitor to Dublin upon the airy summits above Killiney Bay; but in some spots the granite itself has assumed a gneissic character through pressure subscquent to consolidation. On this point pp. 496-502 of the present {memoir may be commended to workers in metamorphic areas; especially noteworthy is the insistance that the formation of cracks at right angles to the direction of flow, so often seen throughout the elongated constituents of a rock deformed by pressure, will serve under the microscope to distinguish cases of secondary from those of primary and igneous flow.

Among the interesting series of conclusions, we may remark how the soda-lime felspars predominate over the potash varieties in the Leinster granite. This only confirms what microscopic examination has taught us of a host of "granites"; so that we may have to fall back upon the comfortable definition of the rock as consisting of "quartz, felspar, and mica," unless we are willing to hand over many old acquaintances to the increasing group of the quartz-diorites.

Although the author states that we have no trace of volcanic ejectamenta emanating from the Leinster granite, we should be inclined to connect with it the great series of Ordovician "felsites," and associated tuffs stretching along its flanks from Wicklow southwards. Volcanoes characteristically break out upon the margins of an up-lifted area, not upon its crest, where the eruptive energy may be presumed to become less and less; and highly silicated lavas, ancient obsidians and pumiceous tuffs, abound among the Ordovician rocks of Leinster, probably as the direct precursors of the granite.

Contributions such as these furnished by Prof. Sollas will be estimated at their full merit by those familiar with the Jong processes of isolation and analysis. The work of careful weeks may occasionally come before us in a page; and the results may appeal more immediately to the philosophic chemist and the crystallographer. But from such a memoir, as from that recently presented to the Geological Society by Messrs. Marr and Harker, we may learn what work lies before us even on familiar granite fells; and we may turn with renewed zest from the streets of Dublin to its highlands, to the moorland white with hoar-frost, and the broad glens reaching to the sea. G.C.

HE interest to outsiders in the plants of Warwickshire lies in the fact that we have here a typical English Midland county, the botany of which is not in any way affected by proximity to the sea or high mountains. Although it is the central county of England, and forms the watershed of the Severn. Trent, and Thames, no portion of its surface rises above 885 feet. Its area is 885 square miles, or 566,458 acres, and it contains 4 hundreds, 2 cities, 1 county town, 10 market towns, and 209 parishes. In 1888 the crops of corn, beans, and peas occupied 106,000 acres; green crops, 38,602 acres; permanent pasture land, 312,000 acres; fallow, 8161 acres; and woodland, 16,650 acres. The soils are fertile, but varied, comprising nearly all kinds but these containing chalk and flints. All the southern and south-eastern part of the county is occupied by a strong clay resting on limestone. A soil of similar kind occupies the north-west. Over a large portion of the county, extending from Warwick to its western boundary, are strong clay loams resting on marl and limestone. Westward and south-westward of Warwick there is a strong clay over limestone. About Rugby and in the valleys of the Blythe and Tame are light sandy soils mixed with gravel. The remaining extensive portions of the county consist of a red sandy loam and a red clay loam, resting on freestone or limestone, and sometimes on gravel. The extent of uninclosed land is very inconsiderable, the only extensive commons being those of Sutton Coldfield and Yaningale. The subjacent sedimentary rocks begin with the Cambrian and end with the Inferior Oolite, with a little volcanic tuff with intrusions of diabase and quartz porphyry in the north-east, near Atherstone.

The author of this book. Mr. James Bagnall, is one of the most meritorious and best-known of our working-men naturalists. He lives in Birmingham, and has devoted himself specially for the last twenty years to the study of the botany of his native county, and in the present work the result of his long and diligent labours is carefully summarized. He has taken rank as one of our best critical British botanists, and has been selected by the Linnean Society as one of its fifty Associates, and has been awarded the Darwin Medal given by the Midland Union of Natural History Societies for the encouragement of original research. His fellow-townsmen are justly proud of him, and when the present work was planned, a number of local gentlemen, with Mr. Joseph Chamberlain at their head, undertook to guarantee him against pecuniary loss. There was, however, no need to call upon them, as 430 out of the 500 copies printed were subscribed for before the book was issued.

The work consists of an introduction of thirty-one pages, which contains the needful explanations of the plan followed in the enumeration of plants and their distribution, together with a sketch of the physical geography, meteorology, and geology of the county, the latter No. 1114, Vol.43]