90 ON THE OCCURRENCE OF CHALK 
time of an eruption ates a fissure, the lava of which appears 
at the base. There was some coral on the shores when the erup- 
tion took place, ur evident from imbedded fragments in the 
; but = hs nai — chalk wen to have wate 
« The fine earthy texture of the material is evidence that the 
deposit was not a subaerial sea-shore accumulation, since wr 
sandstones and conglomerates, with rare cicnanel of more 
- pact rocks, are thus formed. Sand-rock making is the pectic 
prerogative, the world over, of shores exposed to ae or strong 
urrents, either of marine or of fresh water. We sh infer, 
ae a “that the san se ra was produced dithers in a con- 
d area, into which the fine materi ach may have 
agen cy of fire in the result cannot “a oved, it is b ean 
improbable, from the — of the mp of chalk, that a one 
have been a hot sprig at the spot occupied by it. 
“That there was se peculiar cineumstances distinguishing 
this from other parts of the reef is evi 
is, if a true conclusion, is to he. however, only as 
one method by which chalk may be made ; for there is no reason 
microsco 
Sissies, or of anything distinct “ organic, in the sere 
The entire absence of any remains of foraminifera must, I 
venture to think, neoisieack, destroy any claim for tie! ‘Ozh 
limestone to be regarded as chalk proper. 
Neither can the Atlantic ooze, rich ‘thoagl it be in coecoliths 
and the s vo of foraminifera, be regarded as chalk. It is true 
very — one. When conso converted 
land, instead of forming a brilliant white chalk a 
compact — or ates: slaty limestone may be 
e true white o familiar to Englishmen is found over 
an area csesileng from the southern part of Sweden ux, 
a in round num miles, and again the 
Lam, of co gprs nt merely of the soft 
white Ii Serene known tically as chalk, wae to the areas 
etiam Sen eine ee 
a = eS Cee 
