Igneous Ejections, Volcanoes. 107 
a 
among the trap hills (dolerite) of Meriden, called the Hanging 
Hills, and part of it is amygdaloidal. The same is found also 
in Nova Scotia. An examination of a specimen from the 
vicinity of Saltonstall Lake, by Prof. O. D. Allen, shows the 
presence of 4°58 per cent of matter driven off on ignition, after 
deducting the hygroscopic moisture (0°60). It indicates the 
presence of some hydrous mineral (chlorite apparently), in 
place of part of the augite or feldspar. But the percentage = 
rs. 
o . . 
cular trap (now amygdaloidal), is that which is hydrated, 
renders it rather probable that while zeolites and ealcite may 
ve been later made within the rock by superficial action or 
* On this taking in of moisture by liquid rock, Mallet, speaking of the lava in 
the conduit of a crater, makes the fenlowing remarks: “ Within a few years it has 
proved that capillary infiltration goes on in all porous rocks to enormous 
an . 
Proof against the return through them of gases or vapors. So that the deeply 
Seated walls of the ducts Tooting to the i if of such material, may be red hot 
; (like th 
and yet continue to pass water from every pore (like the walls of a well in chalk). 
which is off into at cannot b —< 
down, and must reach the surface again, if by the duct and crater, over- 
Coming in its way whatever o ctions they may . 
Temarka bstructio may be fill ‘ : 
ble property of capillarity sufficiently shows how the lava—fused be = 
pate at or above the level of infiltration—may become interpenetrated throug - 
its mass by steam bubbles, as it usually but not invariably is found to be. 
