258 



THE GEOLOGIST. 



of Calcareous Grit), the Cornhrash and Forest Marble, and the Fullers' 

 Farth, and Inferw^ Oolite are all left out. 



I could point out many other mistakes ; but I think that the above are 

 enough to show that Professor King's Table needs to be a little more 

 '•revised and corrected" before it can be said to be "up to the present 

 time." I would however remark that the good notion of giving separate 

 columns for marine and freshwater types is in great measure marred 

 by the formations in one column being printed on the same line with those 

 in the other, as if they were exactly of the same age ; whereas such is not 

 always the case. Thus, the Eocene Series (in which, by the way, the 

 main divisions of Upper, Middle, and Lower are not given) should stand 

 as follows, — classing the Hempstead Beds with it, and not with the 

 Miocene : — 





Marine Types. 



Fresh- and BracMsh-water Types. 



Upper Eocene . 

 Middle Eocene 



Lower Eoceue , 



< Parts of the Fluvio-marine series of ) 

 (tlie Isle of Wight j 



Upper Bagshot Sand "j 

 Middle r Barton Clay 1 Bagshot 

 Eagshot I Bracldesham Beds | Beds. 

 Lower Bagshot Sand J 

 London Clay. 



Woolwich and Reading Beds (part of) . 

 Thanet Sand. 



Hempstead Beds >| Fi^^^o-marine 

 Bembridge Beds 1 ■ . , , 

 Osborne Beds ffif Air If 

 Headon Beds J ^^^^ °^ 



("Shell-beds of Woolwich, etc., 

 I Pebble-beds ot Broniley, etc. 



In this form the table shows, at a glance, that there are no purely 

 marine formations of Upper Eocene age in Britain ; but that there are 

 beds of that age that are mainly of freshwater origin, etc. 



I am, yours truly, 



W. W. 



The Trinidad Pitcli Lakes. 



SiE, — I observe in a paper " On the Torbane Mineral Field," by Mr. 

 Taylor, in the February number of the ' Geologist,' a statement to the 

 effect that the Pitch Lake of Trinidad stands in close proximity to a vol- 

 cano. As this statement has been repeated in various works, and has ap- 

 parently led to some false generalizations, it may perhaps be well to make 

 the true state of the case a little better known. 



No volcanic substances or erupted rocks have been found to exist near 

 the Pitch Lake ; and not only is there no volcano in Trinidad, but, so far 

 as I am aware, no traces have been discovered either of ancient or of re- 

 cent volcanos in the island. What may perhaps have given rise to the 

 statement above alluded to, is the existence of several so-called mud vol- 

 canos, or salses, which eject only mud and water, and do not possess a 

 tomporaturc above that of the air, and certainly do not appear to have any 

 coiHicction with a\ hat is usually understood by volcanic action. The neigh- 

 bouring parts of South America are equally free from evidences of volcanic 

 disturbance. 



What I have stated may suffice to call attention to the subject ; and for 

 detads. nu'huling an oxcollentand lucid account of the bituminous deposits 

 \\\ Tnnidad and their probable origin, I would beg to refer those desirous 

 of knowing more on the subject to the "Report on the Geology of Tri- 



