RASTALL : THE INGLETONIAN SERIES OF W. YORKSHIRE. 99 
and other easily recognisable rock-types, in addition to the 
usual more or less angular fragments of quartz and felspar and 
flakes of mica. 
Conclusion. 
A detailed examination of the various rock-types included 
in the Ingletonian series indicates clearly that the material 
of which they are formed has been derived from the denudation 
of an area of igneous and metamorphic rocks, chiefly of a schistose 
and gneissose character, but comprising also a variety of intru- 
sive and extrusive rocks. The occurrence of a high degree of 
dynamic metamorphism is of considerable significance, since it 
suggests that the origin of the sedimentary material is to be 
sought in an Archaean complex, which was exposed to denuda- 
tion during the period in which the Ingletonian rocks were formed. 
As we have already seen, the petrographical character of the 
rocks lends no support whatever to the suggested correlation 
with the Borrowdale series, and the apparent conformity of the 
Caradocian rocks on the Ingletonian is probably deceptive. 
All the available evidence suggests that these rocks are far 
older than the Ordovician, and their equivalents will doubtless 
eventually be found in one of the known groups of pre-Cambrian 
sediments, the Torridonian or parts of the Longmyndian,* or the 
Sparagmite of Norway. With the evidence at present at our 
command it is impossible to go further than this. 
In his Presidential address to Section C of the British Asso- 
ciation at Birmingham, Professor Bonney drew attention to the 
wide prevalence of fragments of crystalline and gneissose rocks 
in the later pre-Cambrian and Cambrian grits and conglom- 
erates, and this points to the exposure of an Archaean mass over 
a large area. The portion of the Archaean complex from which 
the material of the Ingletonian rocks was derived must have 
been close at hand, since the fragments are in many cases too 
large to have been carried any great distance, and there is gener- 
ally indication of rapid deposition in shallow water. This 
* It is interesting to note that so long ago as 1874 Mr. Aveline remarked 
on the similarity between these rocks and parts of the Longmjmd series. 
•Goodchild, Geol. Mag., 1892, p. 299. 
