HUDLESTON: EXCURSION. 
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result of precipitation in an inland sea, or at any rate of deposits 
due to streams charg-ed with carbonate of lime and sulphate of 
magnesia ; when, as Sterry Hunt has endeavoured to show, dolo- 
mite and gypsum would be the products. Prof. Green thinks that 
the palseontological facts noted in the Magnesian Limestone of 
Yorkshire favour this view, and he gives a history of the sequence 
of events, beginning with sandy deposits (the quicksands at the 
base of the Permian in South Yorkshire), which pass into sandy 
dolomites, and thence into pure dolomite. The fossils occur 
mostly in the lower beds, and as the waters became more highly 
charged with saline matters, so life became scanty and dwarfed. 
He also looked to volcanic action as a source of supply for mag- 
nesian salts ; but Mr. Lucas pointed out that the requisite 
materials might have been derived from the Yoredale Rocks and 
Millstone Grit of the neighbourhood, which were in all probability 
already above water. These questions have an additional interest 
as bearing on the probable position of the old shore line of the 
Permian sea in these parts, and on the date of the Pennine 
upheaval. 
The Millstone Grit Series is classified by Davis under 
the head of shore deposits with marine intercalations. The name 
serves to show the misleading character of a petrological title, as 
the group is full of shales, often containing ironstone, the .smelting 
of which in former years has much to do with the disappearance 
of wood from Knaresborough Forest. 
In the neighbourhood of Harrogate and Knaresborough the 
upper divisions of the Millstone Grit, including the " Rough Rock,'' 
are wanting, the highest beds now found belonging to the " Third 
Grits'' This circumstance is of course the result of pre- Permian 
denudation, which has not only removed the Coal Measures, but a 
considerable portion of the Millstone Grit likewise. Conse- 
quently, in this district, the Permians repose unconformably upon 
certain quartzo-felspathic grits, which are often of a red or purple 
colour. These are largely developed throughout many parts of 
