The Work of the Geological Survey. 
145 
his inspection. The farmer assists him as he ploughs and drains 
the land. He is even indebted now and then to the gravedigger. 
Every ditch and cutting may be made serviceable for his purposes. 
Wells, quarries, pits, railway-cuttings, in short, every natural and 
artificial exposure of the rocks, or of their detritus, may furnish him 
with the information he requires. It does happen now and then 
that, after fairly exhausting the evidence, he has to confess himself 
puzzled. He cannot be quite sure how the rocks exactly lie and how 
his boundary-lines should be made to run. In such cases we have 
sometimes recourse in the Survey to the boring-rod, and by its 
means we have been able in one or two localities to prove the 
existence of formations of which no superficial evidence could be 
obtained. 
A member of the Geological Survey may start fully accoutred 
for his work in the field without betraying by any outward visible 
token what is his handicraft. His maps are carried in a portfolio 
which slips into his pocket or hangs by a strap inside his coat. His 
hammer goes into a sheath and belt round his waist. His clino- 
meter, compass, notebook, lens, pencils, and other small items are 
easily stowed away among his numerous and capacious pockets. 
Thus lightly equipped he may make his way over any kind of 
ground, ancl can spend a long day in the prosecution of his work. 
Not only by minute observations of superficial detritus, but by 
measurements of the dip of rocks, where these are exposed at the 
surface, the observer may form tolerably accurate conceptions of the 
nature and arrangement of the rocks underneath and of the depth 
at which any given stratum may be expected to be reached. Thus 
in questions of water-supply he may, from such superficial observa- 
tions, predict with some confidence the distance to which a boring 
must be sunk before a certain water-bearing stratum will be 
reached. 
(a) Drift Survey . — Geology had made considerable progress in 
the study of the underlying solid rocks before much attention was 
paid to the looser superficial deposits. The Geological Survey in 
this respect followed the general rule, and for many years made no 
systematic attempt to represent the numerous and often complex 
accumulations of superficial materials. Some of these, indeed, were 
shown on the maps, such as tracts of blown sand and river-alluvium. 
But it must be remembered that in the south-western counties, 
where the Geological Survey began its work, and in those where for 
many subsequent years this work was continued, superficial deposits 
are of such trifling extent and importance that they were not unnatu- 
rally ignored. Only after most of the southern half of England had 
been completed was it determined to map the surface-deposits with 
as much care and detail as had been expended on the older forma- 
tions lying beneath them. It had been discovered that this course 
was necessary both on scientific and practical grounds. In the first 
place, these superficial accumulations contained the records of the 
later geological vicissitudes of Britain, and were beginning to reveal 
VOL. V. T. S. — 17 L 
