178 MITCHELL : drift deposits of the vale of MOWBRAY. 
of erratic rock fragments. I have not confined my observations to 
boulders of large size, but extended them to any fragments, however 
small, which seem interesting as part of the drift. 1 shall first give a 
list, though necessarily an im.perfect one, from a petrological point of 
view. I shall then endeavour to refer the boulders to their original 
stratigTaphical position, mentioning the characters of the rocks or of 
their contained fossils which have guided me in this. Next I shall 
make some remarks on the local distributions of these erratics, and 
the direction of the ice or water-currents by which they were brought 
into the place they occupy. 
I shall begin with the Siliceous Rocks as they form a large 
majority. Fragments of sandstone are present of every size, fi'om 
great boulders to fine sand, of every degree of hardness, from an 
almost flinty rock to stone so soft that it perishes after a very short 
exposure to the weather. In texture they vary from the roughest 
grits to the finest possible sandstone. In colour there is also great 
diversity, while the gi'eat majority are more or less white or pale 
yellow, many are red, and more still are red and white, that is to say, 
consist of white stone mottled with red spots. Some have dark red 
spots on a pink gTOund. In some cases the spots which mottle the 
lighter gTound are brown instead of red. A chocolate colour may also 
be observed, some stones being wholly of a dark chocolate colour. 
Some of these erratics consist of grit, in which are imbedded numerous 
rounded pebbles of white quartz. I have found specimens of chert, 
also of quartzite. In some places there are extensive and thick beds 
of fine loose red sand ; in other places, a yellow argillacious sand is 
present, and here and there I have seen white sand turned up. 
Next in number to the Silicious Rocks are the calcareous masses of 
Mountain Limestone ; they are very common, as are also pieces of dark 
limestone from the Yoredale Series. Magnesian Limestone is very 
plentiful in the gravel of the River L"re. Blue Lias Limestone and 
Oolitic Limestone are among the rocks of the drift. Crystaline 
Brown Limestone, full of encrinite stems, and called, I believe, 
" Yorkshire Marble," is to be found ; and I once met with a large 
piece of pure white saccharoid marble. Of Argillaceous Rocks we 
have fragments of blue and green slates, black shale, and large 
