494 
THE GEOLOGIST. 
mineral crystallizing in veins according to tlic tcmpcratnrcs and precedence due 
to each ; thus quariz crystallizes ih'st, afterwards those the ailinities of which 
hind them most strongly together, and which require kmgcr tinte and lesser 
temperature for becomnig solidified. Yeins running norlli and south, and veins 
running east and west, often containing difl'erent deposits, may be accounted 
for by currents having overlaid each other, and made saturations of distinct 
kinds in any given s])ot ; and this draws me to say that were tlic former forces 
and sources of the euiTcuts calculated, a ])crfeet conclusion might be arrived at 
rcsi)ecting the shape of tlie present contments ; for no doubt the waters have 
depositee! and shaped the lands. At first, when no land broke the surface of 
the globular sea, -wariation of temperature was the only source of its disturbance 
besides tlie tides and the motions of our planet around its axis, so that tliosc 
acquainted vi ith tlie laws of the winds and tides miglit readily surmise which 
had Ijceu the point where tlic greatest accunndation of solid matter took place 
in the sliape of a reef or shoal, and how its first appearance above the level of 
the sea affected tlie then state of things. In contra distmctiou to received 
opinion, 1 sliould say the New World was the first formed, its unbroken coast- 
line showing that the currents were not then so complicated as tiiey are now; 
but if you will give me an opinion on the subject, however crude the idea may 
appear, it may help to elicit facts hitlierto unlhought of. — Your obliged corres- 
pondent, A., Belfast. 
P.S. According to my theory, of course we must look on gi-anite as liaving 
been made from xund and sand from granite, the l)osses into which it becomes 
weathered showing the scams of its deposit plaiidy enongh. The sands of 
Africa and of the otiier desert countries may lie on granite, the upper part of 
which is stiU sand unchanged by igneous agency. 
Phosphate of Lime Nodules. — Deaii Sir, — In reply to Mr. Mortimer's 
letter addressed to you in Number 22 of the " Geologist," I am afraid I 
cannot answer either of his questions satisfactorily ; for I am unable to say how 
the ])lios])hatc of lime was detected in the nodules of the Upper Green Sand at 
Cambridge in the first instance, altliough, as you justly remark, they have 
long been known to contain it. Some of the nodules are supposed to be copro- 
lites, from their peculiar form, and occasionally having scales and other remains 
of fish, &c., embedded in them ; but the majority are, I think, not considered 
to be organic, although tliey yield phosphate of lime ; for 1 believe it is now 
acknowledged that this mineral occurs in rocks more extensively than was ima- 
gined, without being derived fiom bones. When I was at the University, now 
more than twenty years ago, these concretions were known to yield this phos- 
pliate ; but it is only of late years that the green sand has been so extensively 
worked for economical purposes. I have not seen the preparation of the 
nodules for agricultural uses, but I believe tliey are ground down in a mill, and 
in due course, when properly prepared, may be apjjlied as a manure in the same 
way as guano, lime, and oone-dust. I have not written any special paper on 
tliis subject, but in a lecture delivered last January, at tlie winter meeting of 
the Warwickshire Naturalists' Field-Club, held at the Warwick Museum, on 
" The History of Fossil Bone-beds," I suggested the possibUity of the applica- 
tion of the well-known Lias " bone-bed" to this end, and I referred to the value 
and importance of the green sand at Cambridge, and of the Crag in Suffolk, 
from which such large quantities of phosphate of lime are now obtained. 
I lieard that a notice of this appeared in the Mark Lane Express, where it is 
possible Mr. Mortimer may have seen it. — Faithfully yours, P. B. Brodie, 
Vicarage, Rowmgton. 
Fossil Horns from Blue Clay, near Gatehouse. — There was lately found 
in the canal leading from the Bay of Fleet to Gatehouse a pair of iiorns attached 
to a portion of the skull apparcully belonging to an animal of tlic stag species. 
