450 
JOURNAL OF THE PLYMOUTH INSTITUTION. 
THE GEOLOGY OF PLYMOUTH* 
BY R. N. WORTH, F.G.S., 
Hon. Member Plymouth Institution, §c. 
(Read November 25th, 1875.) 
Introduction. 
It is now forty-five years since there appeared in the first volume 
of the Transactions of this Institution an elaborate survey of the 
geology of the country near Plymouth, written by our distinguished 
member, the late Mr. John Prideaux. That paper contained a 
statement of the petrology of the district as accurate as was then 
possible, and still remains in this particular of very high value. 
Written, however, in the very infancy of stratigraphical geology, 
many of its conclusions are to our modern view erroneous, although 
it is remarkable how far in several respects Mr. Prideaux went 
before his time, especially in his identification of the rocks on the 
eastward of the Sound with the Old Red Sandstone, and his 
suggestion of an allied origin between certain rocks then called 
Greywacke and the Greenstones. Furthermore, it was the first 
attempt to systematize our local geology, and entitled to respect 
on that ground also. 
Mr. Prideaux was not alone in these geological labours. A few 
years before he wrote there had been published by another eminent 
member of this society, the Rev. Richard Hennah, "A Succinct 
Account of the Limerocks of Plymouth," which conclusively estab- 
lished what had been strenuously denied — the existence of organic 
remains in our Plymouth limestones. This work was the result of 
years of patient labour, carried on with very few aids, when 
* It will be understood that in this paper the aim of the writer was 
to present a general view of the whole history and conditions of the locai^ 
geology. Much yet remains to he investigated, especially in the important 
department of Palaeontology, which it is hoped may be treated on a future 
occasion. 
