I 
22 IGNEOUS ACTIONS. 
however not a plentiful rock, but forms in a few 
instances, high hills. Mr. Prideaux has noticed a 
most interesting connexion of greenstone with slate, 
in the case of the trapp constituting Rock and 
Estover estates, and the slate surrounding it. The 
slate takes on the colour and partial qualities of the 
greenstone lor some extent.* Prior to noticing this 
in Mr. P’s. paper, I had observed that a portion of 
lime-rock in my neighbourhood, where coming into 
contact with the trapp, had a fine green tinge, and 
though, I then hesitated to believe it to have been 
due to the intrusion and action of this latter rock, I 
now feel emboldened to class the two circumstances, 
as of similar character. I also believe that some 
other phenomena in this county, may hereafter be 
allowed to be ascribable to similar causes, of the 
action of one stratum on another chemically, or 
mechanically, or both. 
From the fact of the great connexion of trapp with 
our fossiliferous strata, it has by some been thought 
entitled to a rank among “ transition rocks”; of late 
however Mr. de la Beche and others, contend that 
this with granite and its modifications—porphyry 
and gneiss, as also serpentine, are collectively to be 
considered as of subsequent date to all other forma¬ 
tions so far as respects their superficial appearance 
amongst the perceptible portions of other strata,— 
in short, that certain subterranean agencies of the 
igneous class have upheaved these rocks into their 
present positions among more recent deposits. This 
rule however, probably does not hold good univer¬ 
sally, for, as we are not bound to compress these 
igneous irruptions into one cera of such disturbance, 
some portions of these Plutonic rocks, may have 
existed in their present forms, anteriorly to the 
* Geological account of the neighbourhood of Plymouth, by 
J. Prideaux, Esq. in Trans, of Plymouth Inst. 
(' / i 
