Marcu 17, 1923] 
NATURE 
353 

existence, his activity may be said to have begun when 
a clear field was given for migration. His rule on the 
earth’s surface was assured by the disappearance of 
continental glaciation from the temperate zones. 
Henceforward, he began seriously to modify the earth. 
The improvement of the entrance to a cave was 
probably his first essay in denudation ; the building 
of a barricade against wild beasts foreshadowed the 
vast works of transport and accumulation that are 
traceable in the Pyramids or in Cuzco. 
By turning up the soil with pointed sticks, and 
later with some primitive form of plough, man assisted 
natural agents in the disintegration of hard rocks. 
As the soil developed under culture, with a constant 
renewal of its air-ways and water-ways, the subsoil 
in humid climates became modified in an opposite 
direction. Its interstices were choked by fine material 
washed in from above. There was a greater retention 
of water in the overlying soil, and acres that at one 
time were liable to run dry became available for the 
continuous growth of plants. When a patch became 
poor and temporarily exhausted, the early and un- 
skilled cultivator moved to some adjacent area, just 
as the Berber of the Tell, with his camel-plough, or 
the Bantu in some forest-clearing, with his wooden 
hoe, is apt to do at the present day. In this way the 
earth was primarily and profoundly influenced by 
man, Let us remember that if our “ civilisation ” 
comes to us from the crowded life of cities, our 
“culture” reaches farther back, and was born with 
the first tillage of the fields. 
This widely spread and continuous attack upon the 
land-surface does not appeal to Dr. Sherlock so much 
as might have been expected. He is more concerned 
with the localised and spectacular results of engineering 
pertinacity in recent centuries. These lend themselves 
to statistical treatment, and they can be compared 
with the slowly cumulative effects of natural, that is 
to say non-human, agents. Dr. Sherlock has brought 
together a large amount of curious information, and 
is able to tell us (p. 24) the total output of coal from 
Great Britain between 1500 and 1913 A.D., the area 
(p. 110) of England and Wales under pavements in 
1908, and the height of the brick structure (p. 236) 
that forms the famous mound of Babylon. A fine 
example of his zeal for calculation appears on p. 73, 
where, by the use of average specific gravities, he 
records the output of quarries of eleven types of 
material during nineteen years in cubic yards in place of 
tons ; 2°75, however, seems a slip for 2-25 in the case 
of gypsum ; and is it scientific to use for quarried 
ironstone a factor so precisely stated as 4017 ? 
It was well worth while to direct attention to the 
enormous bulk of the artificial hills of slag or shale 
NO. 2785, VOL. 111] 
that are still growing in our mining areas. The 
illustrations facing pp. 203 and 207 are convincing 
evidence of the activity of man. The modification 
of an area of complex structure by the spread of a city 
Over it is excellently typified in the chapter on London. 
The story of the origin of Moorfields in water that was 
banked up against the Roman Wall, and of the re- 
placement of the alluvial mud of the Wall Brook and 
the Langbourne Water by the subterranean floors of 
some of our most monumental city buildings, might 
have been told in even greater detail. Dr. Sherlock, 
however, is not to be lured into the picturesque. He 
does not step aside to mention the lining of corridors 
in modern offices and hotels with the spoils of Egypt 
and Numidia, with slabs of imperial porphyry, “ fiam- 
meggiante come sangue,” and with pale marbles volup- 
tuously veined ; or the accumulation of exotic blocks, 
exceeding in variety and length of travel the erratics 
of an ice-age, which man has brought together to deck, 
say, San Paolo fuori le Mura, even in an epoch of 
nineteenth-century restoration. The amount of Caen 
stone in the south of England, or of the corresponding 
eolite from Portland in the grey limestone areas of 
Ireland, suggests similar reflections. A conspicuous 
example of man’s energy in geological transport is 
to be found in the Portuguese stone that was brought 
in carracks round the Cape to build the jutting fort 
on the coral shore at Mocambique. 
Though the reader’s imagination is not touched by 
Dr. Sherlock, plenty of facts are given on which to found 
an outlook. A sense of accurate hard work pervades 
the volume. The material has been quarried out, 
and the result of its accumulation is neither a slag- 
heap nor a cathedral. We have noticed only one 
misprint (“ Berschlag”’ for “ Beyschlag”’), and few 
matters that the geologist could reasonably question. 
We wish that we could agree with the optimistic 
statement on p. 112 that “no sooner is a part of the 
road-covering destroyed than more material is brought 
from a quarry to replace it.” In illustration of the 
denuding effect of ordinary traffic, a photograph of 
one of the deeply cut by-ways in the Folkestone Sand 
of Surrey would have been welcome as a touch of 
rural England. It would refresh one after reading 
of the 156,000,000 cubic yards of comminuted quartz- 
conglomerate on the Rand. 
The construction of the volume is such that its 
main lines suggest attractive by-ways. The amazing 
transference of rock-material for agricultural purposes 
from Chile, Christmas Island, or the desert-edge of 
Gafsa, might well deserve a mention. The de- 
structive action of man-made sulphuric acid in the 
atmosphere of our industrial towns has been pointed 
out by Mr. J. A. Howe. Dr. Sherlock, however, has 
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