DECEMBER 10, 1903] 
NATURE 
n33 
THE SURVEY FORMATION-MONOGRAPHS.* 
|SeSwP es the descriptions of districts and the ex- 
planations of the published maps and sections, 
the Geological Survey has of late years issued treatises 
upon separate formations. In these a full description 
is given of certain geological horizons the survey of 
which has been completed or so nearly finished that 
there is no probability of any important change of 
classification being called for. The subject is ex- 
haustively treated, the palzontological and petrological 
characteristics of the group are described, and its re- 
lation to the equivalent geological deposits on the Con- 
tinent discussed. The work before us is the second | : ] 
horizons from the Bala Limestone to the Crag, are 
of three volumes on the Cretaceous rocks. The first 
volume dealt with the Lower Cretaceous, the second, 
which has just been published, being devoted to the 
Lower and Middle Chalk, and the third, which it is 
hoped will be published this year, completing the 
monograph with a description of the Upper Chalk, 
the discussion of some postponed economical and geo- 
graphical questions, and the full list of Chalk fossils. 
The authors are of opinion that none of the litho- 
logical names hitherto applied to portions of the Lower 
Chalk can be used without confusion or inconsistency, 
and find themselves compelled to seek a more satis- 
factory method of subdivision in the limitation of the 
range of certain species of fossils. Nor do they seem 
to regard with much more favour the use of names 
derived from localities. We must be careful, however, 
in the advance towards fuller knowledge of details 
not to sacrifice precision to consistency. A locality can 
always be found, and when we get there we can 
generally see what an author meant. Fossils are not 
always forthcoming, and from the nature of the case 
frequently turn up where not found before. Moreover, 
the names of fossils are being too often changed. 
Paleontology, in its present phase, is a very useful 
handmaid in geological classification, but a very 
exacting mistress in nomenclature. The zone of 
Terebratulina: gracilis, for instance, is so called after 
a form of doubtful determination, unsettled name, and 
inconstant occurrence. 
It is interesting to follow the authors when they 
point out and explain the changes in the Cretaceous 
rocks as they trace them from one area to another. 
In the south-west, coarse sand and grit take the place 
of chalk, and suggest that we are getting near the 
shore of the Cretaceous sea, and that newer beds crept 
over the older deposits which are seen at the base 
further east, where the land went down first. So 
Barrois has observed that certain beds in the north- 
east of France thin out as they approach the Palaozoic 
ridge, while the Lower Chalk in the south-west is re- 
presented, as in the Sarthe, by sands and sandstones. 
Chemical and mineralogical examination tells the same 
tale. The fine mud, which in Wilts furnishes 16 per 
cent. of the material, increases in the deposits of the 
same horizon as we trace them to the N. and N.E. to 
28 or 41 per cent. Minerals which are well known 
constituents of the granitic rocks of the south-western 
counties occur in the Lower Chalk of the far south- 
west, but have not been found in the corresponding 
beds of the midlands. = 
Many interesting subjects for investigation are 
suggested by an examination of the Cretaceous series. 
The replacement of portions of the chalk by flint might 
at first seem to require only depression to such a depth 
that the temperature of the included water would be 
sufficiently raised to carry silica in solution, while the 
pressure was so great that the chalk-dissolving acids 
1 Memoirs i . me 
‘Cretaceous Ree oe Bae Vor er ates Middle Chalk of 
England. By A. J. Jukes-Browne, with contributi by Wm. Hill. P, 
xili+-568+plates. (London: H.M. Stationery Oncewiges.) aside 
NO. 1780, VOL. 69] 
would be retained in it. But there are other factors 
of which we must take account. The arresting or re- 
tarding of the percolating water had something to do 
with it, as may be inferred from the manner of occur- 
rence of tuberous and tabular flint along the bedding 
and joints, and the limitation of flint over large areas 
to certain horizons so constantly that their abundance 
or absence was long taken as a sufficient indication 
of the horizon. So also the supply of silica from 
spicules in the upper part, or the presence of much 
siliceous sand in the lower part, must be taken into 
consideration. 
Phosphatic nodules, which occur at widely separated 
peculiarly variable in character and mode of occurrence 
in the Cretaceous series, and from their economic value 
and scientific interest call for discussion. Some of 
them are derivative from older beds, and the area from 
which they have drifted has been pretty clearly made 
out, but that only pushes the question into other associ- 
ations; the difficulties remain. There is generally 
evidence of a change in conditions of deposit where 
they occur, but it does not often point to a stationary 
period when animal life was abundant and sediment- 
ation slow, which appear to be the conditions required 
in explanation. 
The name clunch is applied to any challx which is 
used as a building stone, whether it is obtained from 
the firmer beds in the marl, or from the Tottern- 
hoe stone or even from higher horizons. Where the 
Totternhoe stone is accessible it is preferred. It has 
been largely used at Ely, Burwell, and elsewhere for 
internal decorative work, and if cared for has often 
lasted wonderfully, even where exposed to the action 
of the weather. Near Reach it has been quarried from 
Roman times, as proved by its having been used in the 
basement of the Roman villa found near the railway 
east of the village. 
The Red Rock of Hunstanton, &c., does not find a 
place in this volume, because it was not considered 
to be part of the Lower Chalk, but was regarded as 
the representative of the gault, and was accordingly 
described in the previous volume. Other red beds, 
however, occurring at higher horizons in the chalk are 
duly noticed. The Lower Greensand, which is green 
in borings, is foxy-red or yellow at the outcrop. This 
is clearly due to the percolation of water from the 
escarpment. There is much to suggest that the Red 
Chalk of Hunstanton may have sucked up the colour 
by capillary attraction from the underlying Car-stone. 
The red colour does not, however, always coincide with 
bedding planes, and the irregular occurrence of red 
beds in the chalk described in this volume is not so 
easily explained. 
The memoir is an able exposition of the results 
which have been arrived at by long and careful worl 
concentrated upon certain definite geological horizons, 
but illustrated by wide observation and study. It well 
supports the prestige of these formation-monographs, 
from which a large and ever increasing public derives 
so much benefit. 
NOTES. 
WE regret to announce that Mr. Herbert Spencer died 
on Tuesday morning, at eighty-three years of age. 
Tue death is announced of Prof. Proust, the French In- 
spector-General of Sanitary Services. 
Tue ships Morning and Terra Nova left Hobart on 
December 6 to go to the relief of the Discovery, now in the 
Antarctic regions. 
