TRANSACTIONS OF SECTION C. 565 
Apatite is very abundant, occurring in small crystals or grains in the ordinary 
granite, or in larger masses intergrown with tourmaline in the pegmatitic veins, 
and is here of a pale sky-blue colour. In many of the cavities it is well 
crystallised, and forms shining, perfectly transparent pale-blue crystals of a size 
up to $ cm. diameter. 
Very remarkable is the occurrence of andalusite and cordierite as constituents 
of this granite, both of them being rare. The former occurs in grains or aggregates 
of grains, which very distinctly exhibit the characteristic pleochroism of andalusite, 
pink and colourless. Cordierite may easily be taken for quartz, being colourless 
in thin sections, and exhibiting no distinct cleavage traces. There are, however, 
several characteristic properties, which also facilitate the identification of this 
mineral in the present case—firstly, the twinning, resulting through penetration of 
three individuals in the formation of a pseudo-hexagonal crystal ; secondly, the 
pleochroic halos of yellow colour, which cannot occur in quartz ; and, thirdly, the 
decomposition products, consisting of felty aggregates of micaceous or serpentine- 
like minerals. In some cases the crystals are entirely altered into decomposition 
products. 
The concretionary patches contained in the granite consist of a fine-grained 
rock of bjack colour, and show quite irregular but sharply defined outlines. 
Numerous small shiny flakes on the fresh surface indicate that mica is a pre- 
dominant constituent. Under the microscope the rock is seen to consist essentially 
of quartz, cordierite, and biotite; accessory constituents are a few crystals of 
magnetite and small crystals or grains of zircon, generally embedded in cordierite 
and surrounded by a pleochroic halo, which by its deep yellow colour contrasts very 
strongly with the colourless cordierite. There is no felspar of any kind, and the 
rock is precisely equivalent to the cordierite-hornfels known from many zones of 
contact with granite. It is therefore evident that these inclusions cannot be 
regarded as products of differentiation of the granitic magma, but as fragments of 
sedimentary rocks altered by the influence of the eruptive mass. 
10. Report on the Movements of Underground Waters of North-west 
Yorkshire-—See Reports, p. 225. 
WEDNESDAY, AUGUST 24. 
The following Papers and Reports were read :— 
1. Exhibition of a Model of the Cleveland Area, showing Glacier Lakes. 
By Professor Percy F. Krenpatu. 
2. The Glaciation of .the Don and Dearne Valleys. 
By Rev. W. Lower Carrer, WA. 
In studying the geological history of the rivers of the Don system, my attention 
was specially directed to the evidences of glacial action in the area, with the object 
of ascertaining whether glaciation had anything to do with the interesting diver- 
sions of the Don, Dearne, and Dove. Certain valleys in the area, also, attracted 
my attention as possessing abnormal features with respect to the present drainage 
of the district, and I began to inquire what their relations might be to an altered 
system of drainage during the Glacial Period. The present paper is an attempt to 
piece together the scattered glacial evidence, and to ascertain the effect that the 
advance of a glacier from the north and north-east would have on the drainage ot 
this district, and how far the present valleys would help to explain the water-flow 
under such conditions. 
