Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. For convenience, the different strata have been grouped into what are called systems, divided from one another by some natural gap or unconformity 3 and the rocks which make up each sys tem are known as formations. It is a curious and interesting fact that nearly all the formations are represented in Great Britain, so that the farming which is conducted on the top of these must be very varied, and must take notice of them all. It is of course in the study of the soil that geology can materially aid a farmer — its formation and mineral composi tion; and every one who has mastered the principles of the science has got a key to the soils of not only this country, but also to all those which have had their rocks mapped out.