GEOLOGY It may be seen from this table that Northamptonshire is built up chiefly of Jurassic rocks (Lias and Oolite), upon a foundation of Upper Palaeozoic ones. It is partially and irregularly roofed over by Quater- nary deposits. The sculpturing of the county into hills and valleys as we now see it, was begun before, continued with interruptions during, and completed after the Pleistocene period. THE FOUNDATIONS OF NORTHAMPTONSHIRE The Mesozoic rocks of Northamptonshire rest upon an old, irregular land surface of Palaeozoic or older rocks, which may be regarded as the foundation of the county. This Old Land Surface has been found, and the rocks composing it penetrated to a small depth, at a few places in the county, by deep borings, and we propose in this section to give a summary of the interesting information thus obtained. Archaean. The Volcanic Period The oldest rocks known in Britain have been named ' Archaean,' and, since the existence of life on the earth at the time of their formation has not been satisfactorily demonstrated, the term ' Azoic ' has been applied to the era of their formation. During late Archsean times Orton in Northamptonshire was the site of a volcano, possibly one of a string of volcanoes extending from Charnwood Forest in Leicestershire, in a south-easterly direction, as far as Cambridgeshire. The Orton volcano poured forth a lava rich in silica, which, could it have been seen in a less altered condition than that in which it is now found, would probably have been called a ' dacite.' As the lava gradually cooled it became devitrified, losing its glassy nature by the development of crystals, and then, or afterwards, was crushed, and took on the form it now has, to which the names quartz-felsite or (perhaps more suitably) quartz-porphyry have been given. The above remarks embody opinions that have been expressed by Prof. T. G. Bonney and others in various papers, and have been arrived at from a comparison of some volcanic rocks found in a deep boring at Orton with the volcanic rocks of Charnwood Forest in Leicestershire, some 25 miles to the north-north-west, and of High Sharpley in particu- lar, and also of both with the old volcanic rocks of the Wrekin and Wales.^ The Orton boring was a trial one for coal, made in Harrington Dale, in 1883-84, by Mr. J. Fleming of Newcastle, and although un-
- Henry John Eunson, 'The Range of the Palaeozoic Rocks beneath Northampton,'
Quart.Journ. Geol. Saf. (Aug. 1884), vol. xl. p. 492 ; 'Deep Boring at Orton, near Kettering, Northamptonshire,' Journ. North. Nat. Hist. Soc, vol. iv. pp. S7-68 ; Hill and Bonney, 'The Pre-carboniferous Rocks of Charnwood Forest,' Quart. 'Journ. Geol. Soc, vol. xxxvi. p. 342 ; T. G. Bonney, ' On the Archaean Rocks of Great Britain,' Report of the Brit. Aisoc, Montreal (1884), p. 537 ; 'Presidential Address to the Geological Society,' Quart. "Journ. Geol, Soc, vol. xli., pt. 2, p. 48. 3
