1848.] AUSTEN ON BEDS CONTAINING PHOSPHATE OF LIME. 261 
inclination is only slight, and it is from this cause that they are 
carried on much further than is represented in Dr. Fitton’s section. 
The beds productive of phosphate of lime in the neighbourhood of 
Farnham are, as everywhere else, confined to the upper greensand. and 
gault ; two seams in each of these divisions are richer than the rest, 
and present nodules almost exclusively composed of it ; but the whole 
of these two masses afford phosphoric acid, and only in less degree 
than the nodules. It everywhere co-exists with green earth, though 
this mineral, when worked out from the rest of the mass, as is easily 
done, does not appear to afford a trace of it. 
Phosphoric acid occurs in the waters of many mineral springs, but 
only in the minutest quantities ; in combination it is equally scarce, 
the metalliferous and earthy phosphates belonging certainly to the 
rarer minerals, so that we cannot suppose the beds in question to 
have resulted from the destruction of strata containing them. Ani- 
mal structures alone seem to contain it in any abundance, and this 
circumstance has obviously prompted the suggestion which has al- 
ready appeared in several quarters, that these nodules are coprolitic. 
Dr. Buckland has shown that these fossil bodies consist largely of 
this earthy phosphate. It has been urged against this, that these 
nodules have not the convoluted forms so marked in the coprolites of 
the lias and in the Juli of the chalk ; this however is of no importance. 
When these upper greensand and gault nodules are rubbed down so as 
to show a section, they constantly present a concentric arrangement, 
as do agates and like bodies where cavities have been filled by infiltra- 
tion. In the instances of the bivalve shells and ammonites which are 
now solid casts consisting of phosphate of lime, we know that these 
forms must have first been enclosed in the sand, that next the proper 
shelly matter was removed, and in process of time its place occupied 
by the earthy phosphate. 
*Though the nodules now under consideration have an internal 
structure which forbids our supposing them to be coprolites, yet they 
have the oblong forms of such bodies, and I am disposed to think 
that the phosphoric acid which these beds contain was originally of 
animal origin (coprolitic matter), at times with the external form 
preserved, as in the nodules, but for the most part broken up and 
mingled with the sand and ooze. 
The beds which contain this calcareous phosphate have since their 
deposition been placed under conditions which must have promoted 
great internal chemical changes. The vast deposits of the chalk and 
whole tertiary series have been accumulated above them ; they must 
have gone down to great depths, and have been subjected for a long 
lapse of time to an elevated temperature. Under one set of conditions 
the substance of the coprolitic bodies, or that of the shells, sponges, 
and wood, may have been removed, and the phosphoric acid may have 
become generally diffused throughout the mass; whilst under other 
conditions the vacant moulds left by these extraneous bodies may 
have been filled by the infiltration of the phosphate of lime. The 
coprolitic bodies are now casts, as are all the other remains ; and when 
VOL. IV.—PART I. x 
