178 
KENDALL : PRESIDENTIAL ADDRESS. 
He found that he could trace the evolution during Lower 
Carboniferous times of both species and genera, and that even 
varietal changes were, to a discerning eye, sufficient for zonal 
purposes. I must not take up your time with an attempt to 
interpret his remarkable results, but I ma}- say that they Avere in 
substantial agreement with views entertained, but, unfortunately, 
not adequately published, long before by Prof. Garwood. 
^Ir. Johns has taken up the subject with characteristic zeal 
and enthusiasm, and has shown us on several occasions how the 
Avonian succession, or rather the upper part of it, is traceable in 
Yorkshire. Dr. Wilmore, also, has dealt in a very thorough 
manner with the area round the middle course of the Ribble, and 
has devoted much care to the study of the microscopic characters 
of the Limestone. 
Some physical problems concerning the mode of and condi- 
tions of accumulation of masses of highl}^ fossiliferous limestone 
have been discussed by IMr. Tiddeman, whose ingenious and attrac- 
tive theory of Reef -knolls has been much discussed at our meetings 
without evoking any decisive consensus of opinion. At the same 
time, however, it has furnished a valuable provocation to those 
vigorous and frank discussions that contribute largely to the 
hearty camaraderie for which geologists are renoA^ned. 
Another and much larger problem is concerned with the 
form and magnitude of the Eastern extension of the Yorkshire 
Coalfield. 
Two Royal Commissions have successively attempted its 
solution. The first had e\4dence before it by Professors HuU, 
Green and Ramsay, as well as from geologists of lesser rank, and 
alternative lines of limitation were adopted, each indicating a 
generous reserve of untouched coal. No very definite principle 
was enunciated to guide the Commission, though one mtness, 
a mathematician, offered a mathematical treatment of the 
problem, the substance of which appeared to be that, as the 
exposed field was roughly half an ellipse having the edge of the 
Permian rocks for its major axis, it should be assumed that this 
was half the coalfield, and by completing the ellipse, we should 
have an approximate eastern boundar}^ of the coalfield defined. 
This sounds very like the old gibe at the mathematical solution 
