J. LeConte—Structure and Origin of Mountains. itt 
zontal pressure; but their hardness and brittleness is such that 
horizontal pressure would have smashed them into rubble; there- 
fore Capt. Dutton concludes the force was not horizontal. B 
would it not have been better to conclude: therefore the strata 
were not then so hard and brittle as now ‘ 
Again, and finally: Captain Dutton objects, that contractional 
theorists give no reason * why lines of thick strata should be lines 
original crust on which the sediments were laid down. This 
not the 
abutments. These ‘two objections, however, are well worthy 
rta 
ogy which ought to, and doubtless will, be used to modify 
the contractional theory as it now exists. 
Of Captain Dutton’s own theory, which he proposes to sub- 
Stitute in place of the supposed dead contractional theory, I 
