840 
[B.N.F.C. 
3. In considering the above interpretations of observed 
facts, we may class the theories for the origin of hullite into 
three distinct groups. These are : — 
(1) . The Igneous Theory (supported by Scouler, Portlock, 
and Du Noyer), that hullite is a glassy substance 
like ‘pitchstone’ or ‘obsidian/ and was probably 
formed during the last stages of the rock’s solidifying. 
(2) . The Mineral Theory (upheld by Hardman, Heddle, 
Gault, and Lacroix) that hullite is a ‘secondary 
mineral’ of the green earth group, and was probably 
formed during the decomposition of the rock, per- 
meated by meteoric waters in the ordinary course of 
rock-weathering, or by hot alkaline waters of telluric 
origin, under special circumstances. 
(3) . The Altered-Glass Theory (presented by Professor 
Cole) that hullite is ‘the altered and hydrated glass 
of the original basaltic ground-mass,’ or ‘a basic 
glass that has become soft and “gummy” by altera- 
tion;’ it was formed in the first place by igneous 
fusion, but has suffered subsequent transforming 
changes. 
There is no' doubt whatever that Professor Cole is correct 
in his surmise as to the identity of the hullite lining the cavities 
of the rock, with the material of the ground-mass, but, with all 
due respect to' his fine treatment of the subject, I am inclined 
to 1 doubt that hullite was in the first place simply a volcanic 
glass ; I believe that this substance was not only hydrous in its 
composition from the first, but that it has not undergone any 
extensive alteration since that time. In its original condition,, 
and as still found in certain portions of the rock, the hullite 
might be more accurately described as a hydrous, waxy sub- 
stance, intermediate in its nature between a volcanic glass and 
a green earth. Professor Cole compares the alteration of the 
original hullite to its present form, to the alteration of basaltic 
glass into a green “serpentinous” material ; but, where the hullite 
is altered, I believe that the change is mostly a physical one, 
and only to a small extent chemical. The resemblance of 
