19* Editorial Comment. 
ply of natural gas accumalating underground at this point. In 
ordinary times it leaks away into the air unnoticed. But in win- 
ter when the ground is frozen and its escape is prevented, it accu- 
mulates beneath the crust until its pressure rises high enough to 
burst it with explosive violence. In this way the cracks in the 
ground, the shock and the loud noise may be fully accounted for. 
In considering this explanation it must be borne in mind that 
gas wells of very moderate yield will, when closed, develop 
an enormous pressure which, however, rapidly subsides on open- 
ing the mouth of the bore-hole. There is also the possibility 
that the gas does not come from the black shale— the usual 
source of Ohio gas — but from some local bed of vegetable mat- 
ter contained in the thick drift of the Tuscarawas valley. Ly- 
ing also at a distance of several miles from any place where the 
product could be used the heavy cost of piping must be encoun- 
tered. These and other similar considerations render it doubtful 
if commercial success would attend any efforts to win gas. Yet 
geologically it would be very interesting to find out the exact con- 
ditions which lead to results so singular, and which have seldom 
if ever been reported elsewhere so far as the writer is aware. 
EDITORIAL COMMENT. 
PROK. JUDD ON THE LAVAS OF KRAKATOA. 
In the London Geological Magazine for January iSSS Prof. 
J. W. Judd discusses the lavas of Krakatoa and compares them 
with those of Santorin in the Mediterranean sea, of Buffalo 
peaks, Col. and of the Cheviot hills in the north of EnglanJ. 
All these consist, he states, of a porphyritic mass composed of a 
colloidal glass}' base with crystals of felspar, enstatitc, augite 
and magnetite. The chemical composition of the base and that 
of the crystals differ but slightly in all these lavas but their rela- 
tive quantity varies from 90 per cent to lo per cent. The na- 
ture of the rock as a whole therefore varies from a distinctly 
acid to a distinctly basic magma. 
Prof. Judd next shows that all the lavas from Krakatoa 
