VI LETTER OF TRANSMITTAL. 



shapes of animal and plant, by which it and its rock strata can 

 be recognized by the geologist. A knowledge of these peculiar 

 animal and vegetable forms is in fact a part of the training of 

 a good geologist in tracing outcrops and discovering the min- 

 eral resources of the Commonwealth ; for every age produced 

 also its own kind of minerals, so that fossils are a guide to the 

 mining engineer, and especially so to the prospector. 



When the geological survey of Fennsylvania was first ordered, 

 its first business was well understood to be not scientific, but 

 practical. It was to study and to find out all about the iron, 

 coal, oil, gas and other mineral resources of the State; and then 

 to inform the citizens of the State better about what they 

 already knew more or less uncertainly or imperfectly, and dis- 

 cover for them what was still only suspected, or wholly un- 

 known. This task the survey has faithfully and zealously per- 

 formed for fifteen years ; and its strictly practical character is 

 acknowledged by those intelligent business men who are the 

 the wealth-producers of the State. The farming population 

 have not so strongly felt its value, because its advantages for 

 them have been indirect, but none the less real. For it is 

 plain to see that a geological survey carried on in a strictly 

 practical spirit must necessarily benefit every man, woman 

 and child in the Commonwealth. It is iron, coal, oil, gas and 

 other minerals which build cities, towns, villages, furnaces and 

 mills; and cities, towns, villages, furnaces and mills furnish to 

 the farmer his principal market ; thereby enhancing the value 

 of his land ; and upon this again depends the welfare of his 

 wife and children. Even if the work of geologists were wholly 

 confined to the mines and quarries, it would still be in the in- 

 terest of the agricultural citizens of the State. But the 

 geological survey has worked directly for the farmers of the 

 State by informing them of what respecting their own fields 

 they could never have found out by themselves. But as human 

 beings breathe air without knowing it, so they obtain knowl- 

 edge without being aware that it does not come directly from 

 their own brains, but from the patient and often painful labor 

 of those w^ho specially devote themselves to the manufacture 

 and distribution, that is, to the discovery and publication of 

 knowledge. 



It is said that the survey has cost the State nearly a million 



