KENDALL I PRESIDENTIAL ADDRESS. 
179 
of earlier and more intricate geological problems — guess half and 
multiply by two. 
The 1901-5 Commission (Lord Allerton's) accepted as regards 
the northern and eastern boundaries a principle well recognised 
by students of Geological Tectonics, that folds of the strata have 
frequently manifested a tendency to accentuate from time to 
time by successive movements, at intervals represented by whole 
geological periods, and in some cases by frequent repetitions of 
the folding movement operating during the formation of successive 
strata. Folding of both types were found to have occurred at 
Market Weighton on a line that seemed to be the easterly con- 
tinuation of the northern edge of the coalfield. The southern 
limit seemed to be indicated b}^ a broad zone extending from 
Charnwood to near Cambridge. The eastern boundary might 
possibly be found on the line of a post -Cretaceous fold running 
through Louth. 
These principles were accepted by the Commissioners, who, 
however, did not adopt the southern boundary suggested and 
proposed themselves one running from Charnwood to the Wash. 
Even thus limited, the hidden coalfield is of majestic dimen- 
sions, and must constitute the greatest of the national coal assets. 
The older Primary rocks have been studied in detaU by Prof. 
Hughes and others on behaK of the Geological Survey, and Dr. 
Marr and some of the later generation of geologists from Cam- 
bridge have added largely to our knowledge of these rocks, in 
which Lap worth's Graptolite Zones have been recognised. 
A notable result has been the recognition by ^Ir. Rastall of 
an Archaean series in Ribblesdale and Chapel-le-Dale. Aveling, 
when mapping in the district thirty years before, had pointed out 
the resemblance of the grits and slates under Ingleborough to 
the rocks of the Longmynd, and his observations are confirmed 
by Mr. Rastall, w^ho proposes to call this series the Ingletonian. 
Many interesting tectonic problems relating to the upbuilding 
of Yorkshire have engaged the attention of geologists especially 
during the last twenty years. Most of these relate to the role 
of the Craven faults and the folds related to them. John Phillips 
drew attention to them in his classical Geology of Yorkshire, 
