PREFACE. XXiil 
conclusions respecting the Devonian System which we had arrived at the preceding year, 
chiefly through my personal labours. Our summer work suffered a considerable retardation 
from a premature attempt (sanctioned by no less a personage than Prof. A. Goldfuss of 
Bonn) to classify the fossils of the Hifel Limestone with those of the Upper Silurian Groups; 
but before the expiration of the summer we escaped from this difficulty; and as our joint 
labour has been published, it would be idle for me to dwell upon it any longer in this Preface. 
For nearly three months during the Academic vacation of 1840, I was confined by 
my duties in the Cathedral of Norwich, and was therefore cut off from any extensive 
field work: but within the limits of the vacation, guided by the Silurian map, I made 
some hasty excursions which brought to the Cambridge Museum what I then regarded as 
a rich harvest of fossils. 
The year 1841 was partly employed by me in studying the Devonian rocks of Ireland 
under the guidance of my friend Sir Richard Griffith; and from Ireland I passed into 
Scotland, still in quest of facts that might give me the means of constructing a classifica- 
tion which would apply to every portion of the older rocks of Great Britain; but neither 
during that nor during any other tour did I find anything to compare with, much less to 
supersede, the magnificent succession of groups which I had seen in Wales and Siluria. 
I resolved therefore to re-examine the whole of my work in Wales, and then to 
perform the same task among the Lake mountains and the districts bordering upon them. 
In this way I endeavoured to bring the several Paleozoic Groups into good co-ordination, 
and to name the lower portion of them in conformity with the system of Cambria, and the 
upper portion in like manner in conformity with the system of Siluria. This task I 
hoped to complete in two hardworking summers; but I found to my cost that I had greatly 
underrated the labour that was before me. 
In 1842, with Mr Sowerby’s permission, I was joined by Mr Salter, as a youthful and 
then joyous fellow-labourer, and especially as one well prepared, to complete the fossil 
catalogues of the several groups which we had to examine. This task employed us during 
two entire hardworking summers. 
At the end of the summer of 1843, we had done our work thoroughly, as I then 
thought; for my previous labours in North Wales enabled me to conduct my young friend 
and assistant to all the localities of principal interest, with small loss of time in seeking 
them out. For a few days in 1842, we were joined by Sir Richard Griffith; and I will 
here state, in as few words as I can, the results of this joint work of two summers. My 
youthful and cheerful companion gradually became a good field surveyor, and he dressed up 
my Sections so as to make them fit for publication, of course on a reduced scale, and 
he was of infinite use in fortifying the conclusions [ derived from my comparative 
