292 MESSRS. A. IIARKKR AND J. E. MARK ON 



deeper-seated magma occur where the above-mentioned normal 

 strike is complicated by the great fractures ranging down the Lune 

 Valley in the neighbourhood of Tebay and Sedbergh. 



We are now confronted with the question, what is the nature of 

 the Shap intrusion itself? It does not appear to be a simple 

 laccolite, and, on the other hand, we have seen that several sills 

 arc protruded from it around the margin. The strike of the rocks 

 may have been bent by the granite, or, on the other hand, the 

 intrusion may liave taken place in a region where a weak ])lace was 

 caused, owing to the bending of the rocks. The usual greater 

 density of tlie altered rocks seems to indicate some compression, 

 though whether this and the preceding cause would be sufficient to 

 leave space for the granitic intrusion is doubtful. 



On the other hand, the abnormal alteration of the rocks around 

 a mass with so small a diameter would suggest the passage of molten 

 matter for a considerable period through the channel which is now 

 tilled with granite, though whether this channel ever communicated 

 with the surface, giving rise to volcanic outbursts similar to those 

 which occurred in regions farther north during Old Red Sandstone 

 times, we have no evidence to show. 



On the whole, the phenomena presented here seem to us to be 

 most easilj' explicable upon the supposition that molten matter was 

 for a long period forced from the underlying magma through a 

 channel which may have been " punched out " in the way suggested 

 by Dr. Ch. Barrels in the case of the Eostrenen granite *, and that 

 it finally consolidated therein in the form of a " cedar-tree " lacco- 

 lite, i. e. in a form corresponding with that of the gabbro shown in 

 the theoretical representation drawn by Dr. A. Geikie f. 



Lastly, in connexion with the deep-seated magma, one naturally 

 recalls the magnetic observations of Profs. Thorpe and liiickeri on 

 the occurrence of a " ridge " in the neighbourhood of Appleby ; but 

 when we consider the subsequent injections of more basic rock in 

 the neighbourhood, such as the Great Whin Sill, which was also 

 doubtless connected with deeper masses of a somewhat similar 

 nature, wc are not inclined to lay much stress upon the coincidence. 



§ lY. MeTAMORPHISM or the SuREOtrNDING E-OCKS. 



A. The Andesitic Group. 



The lowest rocks affected by the granite intrusion are those 

 which may be classed as andesitic. Owing to the anticlinal folding 

 described above, this group occupies a considerable area of ground 

 to the north and west of the granite, being in contact with the 

 intrusion around one-half of its circumference. The total thickness 

 of the andesitic lavas is probably made up of a succession of com- 

 paratively thin flows : this is inferred from the fact that the rocks 



* Ann. Soc. Geol. du Nord, vol. xii. (1885) p. 105. 

 t Trans. Roy. Soc. Edin. vol. xxxv. (1888) p. 142. 

 + ' Nature.' ko\. xh. p. 598 (April 24tb, 1890). 



