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POPULAE SCIENCE EEYIEW. 
HOW TO MAKE A OEOLOGHCAL MAP. 
By HORACE B. WOODWARD, F.G.S., 
Of the Geological Sijryey of England and Wales. 
[PLATE XCIII.] 
A mong the numerous efforts to popularise Geology, we are 
not aware that much has been done to explain the 
mystery of geological maps. We say mystery, because by 
many they are looked upon as a sort of scientific myth ; they 
are rarely understood by any but the geologist proper, and cer- 
tainly are but little known and appreciated by our agricultural 
and “ practical ” population. Of course to make the best use 
of^ our geological maps a considerable knowledge of the science 
is necessary ; and if this were the case, we should not hear so 
often of fruitless efforts to find coal. The notions that black 
shales are an indication of coal, and that “ where God has sent 
iron-ore. He has also sent coal to smelt it,” have not died out, 
anymore than has that relic of superstition, the Divining-rod, 
which in the W^est of England has still a few credulous prac- 
tisers. But the meaning of geological maps may be under- 
stood without any very deep knowledge of geology. It is 
frequently remarked that such a map “ looks very pretty with 
all those colours, but how do you find it out ? ” To say a few 
words about the construction of geological maps, and what they 
mean, may therefore be of some interest ; and in doing so, we 
may at the same time draw attention to a few of the practical 
bearings of geology. 
In our own country we are well provided with geological 
maps, from the small atlas edition to our Government Survey 
Map, which, however, is not yet completed ; and if it were, the 
map of England and Wales would measure about 36 ft. in 
length by 25 in breadth ! It was about two hundred years ago 
(1673) when the first suggestion for a geological map of Eng- 
land was made by Dr. Martin Lister. Geology was then little 
known except as a mineralogical science, and fossils were 
either “freaks of nature,” or the results of some “plastic 
virtue ” in the earth. It is therefore interesting to consider 
