40 
JUNCTIONS WITH OTHER ROCKS. 
or less cemented, blended together and intermixed, 
appears to me to have attracted too little notice, for 
though, in some cases their admixture seems ration¬ 
ally accounted for, by the previous well-founded 
conjecture, that their deposition was coeval, there 
are other instances, in which we have no ground for 
imagining that their depositions were coetaneous. 
Lime and slate are most freely intermixed at their 
points of junction, and we see the same thing occur¬ 
ring between the slate and sandstone in spots where 
these meet, the latter frequently being wedged into 
the other ; in some places also, there being alterna¬ 
tions and union of qualities (arenaceous schist) 
for a considerable area, there are other reasons for 
imagining the contemporaneousness in the deposit 
of these strata. On the other hand, where slate 
abuts against granite or trapp, we find, that in some 
spots the former is cemented freely to the latter. 
This is seen in numerous blocks scattered profusely 
through the valley at Ivybridge, and I am sensible 
of cases where there is as thorough intermixture, as 
between slate and limestone. 
Amongst the varied relations assumed by slate in 
its beforenamed general diffusion, there is one which 
seems to indicate, that even the oldest (allowing for 
argument that they are of different ages) kinds were 
not contemporary with granite, for this rock not only 
extends into contact with granite at our north, but 
even spreads between the hills of that primitive 
formation, assuming perhaps in its run, a lengthened 
three-sided figure. Whatever be the actual relations 
between lime and slate, (or at least certain sorts of 
the latter,) and whatever may be the depth to which 
the lime as a whole, or in some parts descends, I 
must not omit to furnish an additional proof of the 
intimate connexion subsisting between these two 
strata, namely, that “ Lime appears in masses on 
the north,south, and west sides of the Dart,insulated 
