708 YP LD DINGS 
ration of the bottom of the igneous mass, it seems quite probable 
that the magma spread in the shaly beds at the base of the 
Cambrian strata immediately over the nearly horizontal surface 
of the gneiss and beneath the laccolith already mentioned. The 
Ideal section of the Holmes bysmalith. 
thickening of the laccolith to the north and its contact with gneiss 
to the east may have hindered the further spreading of the 
later magma, resulting in a rupture of the overlying rocks in a 
block which.was lifted by the intruding magma. The area of 
the block was more than five square miles and the vertical dis- 
placement more than 2000 feet, probably more than twice that 
height. Owing to the nearly uniform, crystalline character of 
the rock constituting the Holmes bysmalith, the grain being larger 
than that of the rock:of the adjoining laccolith, there is little 
doubt that it solidified beneath a covering of strata. The slope 
of the planes of contact indicate that the intruded body possessed 
a steep dome shape, and the nearly horizontal position of the 
surrounding sedimentary rocks, at a little distance from the 
igneous body, prove that the arching of the strata took place at 
