74 The American Geologist. Ausust, L903. 
rapid cooling was originally a spherulitic tachylite, and has 
become devitrified by slow secondary action. Yariolite stands 
in the same relation to the basic lavas as pyromeride does to 
those of acid character."* Gregory concludes from his study 
of the Berneck variolite in the Fichtelgebirge, that, "though the 
varioles be the product of rapid cooling, too sudden a solidi- 
fication of the diabase may prevent their formation. For a 
similar reason the amygdaloidal is less variolitic than the com- 
pact diabase, the loss of water that occupied the vesicles having 
diminished the fluidity of the rock."i A review of the literature 
dealing with variolite seems to show that it is best developed 
within "ellipsoidal" or pillow-lava, though a goodly number of 
instances are on record showing that the structure may appear 
just inside the glassy selvage of quickly cooled diabase dikes. 
In the paper of Cole and Gregory just quoted there will be 
found a full set of references to the previous investigations of 
variolite. | In Xorth America, two occurrences, both in pillow- 
lava, in addition to this one from Newfoundland, have since 
been described by Ransome § and Clements. || In Europe sev- 
eral new localities have afforded examples of the rock. Cole 
has noted variolitic diabase in Anglesey!! and in County Down, 
Ireland; Sollas, variolitic diabase in Wicklow County, Ire- 
land/ and Miss Raisin variolitic pillow basalt from the Lleyn, 
Wales. " 
The phenomena at all these localities seem to bear out the 
general conclusions of Cole and Gregory. Although there is 
but little direct microscopic or chemical evidence on the point, 
it seems justifiable to apply their explanation of the variolitic 
structure to the Newfoundland rock. The identity of decom- 
position products in variole and matrix certainly argues against 
any significant chemical differentiation in the magma at the 
time of variole-formation. 
The Origin of the Pillow Structure. — In the latest import- 
ant publication on pillow-lava, Clements has given a useful re- 
view and bibliography of the subject. He has considered the 
* Quart. Jour. Geol. Soc. London, vol. xlvi, 1890, p. 331. 
I Ibid., vol. xlvii, 1891, p. 61. 
i Op. cit., p. 327. 
5 Op. cit.. p. 99. 
j Monograph U. S. Geol. Surv., vol. xxxvi. 1>99, p. 10S. 
Proc. Rn\- Dublin Soc, vol. vii, 1891, p. 112. 
Ibid., 1892, p. 511. 
' Ibid., vol. viii. 1893, p. 94-. 
" Op. cit. 
