132 BALDERSTON : THE SILURIAN ROCKS OF INGLETON. 



4. That the quartz bands and veins usually seen in the galliards r 

 and less frequently in the slates, pass in any direction and 

 irregularly along the course of faultage, shrinkage, and other 

 cracks indiscriminately, but that the quartz bands of the 

 true trap-dykes of the Green Slate series run in parallel 

 lines, at regular intervals, across the faces of such dykes, as 

 the result of a single uniform cause, shrinkage or cooling 

 and filling of the consequent cracks. 

 It may still further be remembered, that had any great bulk of 

 the galliard element been thrown up in the form of dykes, we should 

 naturally be led to infer that the thickness of the stratified series 

 would not so nearly correspond on each side of the fold, as it 

 evidently does. A few may have been lava-flows or intrusions inter- 

 bedded prior to contortion, so as to have participated in the 

 subsequent folding. As a whole, the galliards, in many respects, 

 differ essentially from most of the genuine dykes found here, but do 

 so in a less degree when compared with the undoubted felstones, a 

 class to which they more nearly approximate, and one which was 

 perhaps ejected nearer the time of the deposition of the beds amongst 

 which they are found. 



Among the twelve dykes described, three, if not four varieties of 

 trap may be recognised, Nos. 1, 2, and 3, forming one group, with 

 the first slightly divergent from the other two. The next group 

 consists of 5 and 8, the constituents and appearance of these 

 rocks allying them to the darker hued and less acid division 

 of the Helmsgill dykes, which possibly have too great a proportion 

 of orthoclase to be regarded as true kersantites. The third group 

 is comprised by the series described as number 9, and this possibly 

 may be a very compact and much altered kersantite, but at some 

 points there is a considerable presence of quartz as a porphyritic or 

 accidental constituent, and on the whole exact identification is 

 difficult. The last division comprises Nos. 4, 6, 7, 10, n, and 12, 

 which are felstones, slightly hornblendic and containing a little mica, 

 more especially on, or near the surfaces of joints. The sub-marine 

 lava-flows belonging to No. 4, differ little from the Great Dyke itself, 

 but may be regarded as felstone rhyolite, the four beds being almost 

 synchronous and evidently due to one eruption. 



The total number of exposures of the Traps of the subjoined 

 list is more than fifty-five, and of these, nearly half belong to the 

 Great Black Dyke, which has not yet been described. 



The Galliards, or ' sub-aerial traps ' of Ingleton Dale, I have 

 grouped among the sedimentary rocks, whatever may have been the 

 origin of their ingredients, and my doing this may be regarded as 



Naturalist, 



