848 ELEMENTARY GEOLOGY 
Sometimes these dykes spread out between the layers 
of sedimentary rocks, forming intruded sheets (Fig. 211), 
like the Palisades of the Hudson, and East and West 
Rock of New Haven, Connecticut. Again they break 
Fig. 211. 
Diagram to illustrate intruded sheet. 
great, irregular cavities deep in the earth and fill them 
with lava, which upon cooling, forms a bosse of plutonic 
, rock, like granite 
(Fig. 212). 
Sometimes intrud- 
ed lavas bend the 
layers of rock above 
them into the form 
of a dome, filling the 
space with lava (Fig. 
213). These are 
known as_ Jlaccolites 
(or laccoliths), and are really volcanic eruptions that 
did not quite reach the surface, but elevated the rocks 
instead of breaking them. They are found among 
the mountains of Colorado and in the Henry Moun- 
tains of Utah. 
Fie. 212. 
Diagram to illustrate bosse of intruded rock B. 
