92 OUTLINES OF FIELD-GEOLO PART I 



valuable his s< i the field. Part of his training 



should consist in the study of as good a series of 

 typical fossils as he can consult. He ought to fami- 

 his eye with the leading genera and more charac- 

 teristic species of each geological system and formation. 

 Knowledge of this kind, so portable when carried in the 

 head ready for use, so bulky and difficult to transport and 

 use when contained in many learned volumes, enables 

 him to decide for himself as to the geological horizon of 

 the formations. Should he be in doubt about the deter- 

 mination of his fossils, he must submit them to an expert 

 in the subject. 



1 or many purposes of field-geology it is not absolutely 

 necessary, though it may be very desirable, that we should 

 know the names and the zoological or botanical grade of 

 the fossils. What we need to know in the field is that 

 certain organic remains, whatever be their nature or 

 names, occur in particular beds of rock. We should be 

 able to recognise them and use them as indices to mark 

 out the strata, and thus to fix our geological horizon. 

 William Smith, by whom this stratigraphical use of fossils 

 was originally taught, knew little of the nomenclature or 

 natural history of the fossils he dealt with. But he learnt 

 to recognise them, and to judge accurately of their 

 position in the geological series, and he made as admir- 

 able use of them in tracing the outlines of the develop- 

 ment of the Secondary rocks across England as if he had 

 been able to name and describe each species. Geology 

 has made vast strides since his time. Though the field- 

 geologist may use the fossils without any scientific know- 

 ledge of them, the sooner he obtains that knowledge the 



