Geological Society of London. 43 
for supposing to be due, not to the action of the lightning, but toa 
pre-existent segregation of sphene. 
The occurrence of globulites, margarites, longulites, and micro- 
liths in the glass would seem to indicate a less sudden cooling than 
is assumed to be usual in such cases ; for the glass presents no signs 
which would characterize a subsequent devitrification or secondary 
change, and the bodies just enumerated appear, unquestionably, to 
have been formed during the refrigeration of the fulgurite. 
3. “On the Occurrence of a New Form of Tachylyte in Association 
with the Gabbro of Carrock Fell, in the Lake District.” By T. T. 
Groom, Hsq. Communicated by Prof. T. McKenny Hughes, M.A., 
F.G.8. 
In this paper the author described an ancient but well-preserved 
glassy rock of basic composition which he had found as a vein 
associated with the gabbro of Carrock Fell. The rock was described 
macroscopically and microscopically, and a complete chemical 
analysis was given. The chemical composition resembled that of the 
more acid basalts and the augite-andesites, and approached especially 
closely to some continental basalts, analyses of which were added 
for comparison. Examined microscopically, the rock consisted of a 
globulitic and crystallitic glass-basis of green colour, containing 
spherules of quartz, spherulitic felspars, and an interesting series of 
granules and granular aggregates of augite, which likewise frequently 
assumed a spherulitic form. The rock was rendered microporphy- 
ritic by the sparing development of crystals (or skeleton-crystals) of 
plagioclase felspar, augite and quartz. The optical characters of 
each of the minerals were given. Owing to the mode of develop- 
ment and to the variety of its constituents, the rock possessed an 
exceedingly complicated structure. The order of crystallization was 
worked out, and it was pointed out that a second generation of each 
of the important constituents had arisen. The second generation of 
felspar was of a more acid type, and that of the quartz was devoid 
‘of fluid vesicles, and had crystallized out after the rest of the rock 
had solidified sufficiently to form cracks. Close physical and 
mineralogical relations with the gabbro were indicated, and the 
author had no doubt that the two were in actual connection with 
one another. The age was put down as probably Ordovician. A 
comparison of the rock with other basic rocks showed that it had 
affinities both with the glassy forms connected with the more 
voleanic members, and with the variolites of Durance found asso- 
ciated with diabase. The relation with the latter rock was espe- 
cially marked, but important points of difference rendered a separa- 
tion of the two necessary, and for the new type of rock thus 
recognized the name Garrockite was suggested. This rock might 
be looked upon as a Quartz-Gabbro-Vitrophyre. 
