TATE: YORKSHIRE PETROLOGY. 
1. — The Lamprophyres. 
(1) 111 the picturesque dales lying at the foot of Ingleborough, 
the Ordovician system is represented by its middle and upper series — 
the Borrowdale and the Coniston Limestone Groups — in nearly 
vertical position, with the mountain limestone resting upon their 
upturned edges. After the Chapel-le-Dale Beck has flowed past the 
last green slate quarry, on its way to that charming health resort, 
Ingleton, it cuts through a felspathic ash-bed, the latest member of 
the volcanic series. The physical transition is indicated by the 
presence, above and below this bed, of sedimentary deposits consist- 
ing of yellow micaceous sandstones and shales, the latter gradually 
acquiring a calcareous character, until finally capped by the fos- 
siliferous Coniston Limestone, and its superimposed calcareous shales 
extending as far as the northern fork of the Craven fault. Jutting 
out boldly into the stream, from the receding contorted shales 
forming its left bank, we meet with a rock of some historical 
interest, as it was first described by Philips in 1832, and is the only 
one of our series that he deemed worthy of special notice. " The 
composition of the stone," he says, " is remarkable and uncommon. 
It is a fine-grained crystallised compound of red felspar, light- 
coloured hornblende and mica, occasionally holdmg large masses of 
the same red felspar, with broad flakes of mica in them. It may as 
well be called hornblende granite, or micaceous syenite as green- 
stone." This brief, but clear, account of its macroscopic appearance, 
while it leaves little now to be added, impresses one with the high 
degree of culture to which the observing eye had been trained by the 
fathers of geology, long ere the resources of microscopical science had 
been called in to solve its problems. The rock forms a nearly vertical 
dyke with parallel walls, intrusive in the contorted calcareous shales. 
The dyke, as is common to our series, can be traced only for a few 
yards continuously ; at low water, it is seen to end abruptly along a 
joint-existing prior to its intrusion. It is about 8 feet thick, and 
presents a bold mural face to the south some 9 feet high ; an 
additional 4 feet below being descernable in the water. 
Macroscopically, hand specimens shew a small-grained reddish- 
brown rock of uniform texture, enclosing nests of somewhat larger 
