3i7 



Guppy Reprint 



169 



So much by way of introduction. I will now turn to the 

 subject I have to bring before you today. 



In order more easily to recall to your minds the relative 

 position in the earth's crusts of the strata developed in this part of 

 the world, I have here a rough diagram in which the strata I am 

 referring to are distinguished by colours while those which are not 



Page 25 



represented here are left uncoloured. On this diagram I have 

 shown our oldest strata, those of the northern hills, as being be- 

 tween the carboniferous and devonian. This is a sort of com- 

 promise to represent the uncertainty of our knowledge of the ex- 

 act age of these formations, for up to the present time we have 

 failed to find any very satisfactory evidence of their age. The 

 geological surveyors of 1859 nowhere distinctly state an age for 

 these formations, but it may be inferred from w T hat they say in 

 the geological report and from what Wall says in his paper on 

 Venezuela that they were inclined to consider that they are of 

 paleozoic age. Until now I have so treated them. My friend, 

 the late Ralph Tate, Professor of Geology in the University of 

 Adelaide, thought that they might be jurasic. I infer from what 

 Mr. Cunningham Craig says about them that he leans to a cre- 

 taceous age for these rocks. On looking over the evidence, how- 

 ever, I cannot think that they are younger than carboniferous. 

 The only paleontological evidence is that found by me, except a 

 Rhynconela mentioned by Mr. Cunningham Craig which I have 

 not seen. But that brachiopod genus ranges from the Silurian to 

 the present time, so it can hardly be said to have any decisive ef- 

 fect upon the question. In a paper read by me to the Scientific 

 Association of Trinidad in 1877 I gave an account of the older 

 rocks of Trinidad and referred to a previous paper which I had 

 communicated to the Geological Society of London on the sub- 

 ject. I gave a list of the fossils I had discovered — a very small 

 list of imperfect specimens, but which, so far as it went, was in 

 favour of the paleozoic age of these rocks, as was admitted by W. 

 O. Crosby of Boston in reviewing my work on them. From the 



