TO 
DAVIES GILBERT, ESQ. 
D.C.I.. (by diploma), F.R.S., HON. M. R. S, E., HON. M. R. I. A ., 
F.S.A., F.I,.S., F.G.S., F.R.A.S,, ETC. FTC. 
MY DEAR SIR, 
I ONLY fulfil a gratifying duty in dedicating 
to you the present Essay, which owes its 
existence principally to your favourable opi- 
nion of my ability to discharge the trust 
confided to me. 
To have been thus selected for such a ser- 
vice, is a distinction which I prize, as one of 
the most honourable results of my devotion 
of many years to the study of the mineral 
structure of the Earth. I fear, however, that 
your estimate of my qualifications has been 
raised above my deserts, by your affectionate 
regard for the University, with which it has 
been our common happiness to be so long- 
connected. 
GEOL. b 
