CORRESPONDING SOCIETIES. 531 
be no other evidence. In regions where there are deposits of the Glacial Period, 
observations on the pebbles are also most important. 
In this connection geologists on the coast should not overlook the stones which 
friendly fishermen may bring home in their trawls. Some years ago a new fossiliferous 
Tertiary formation in the bed of the North Sea was thus discovered through the 
fishermen from Aberdeen. On the Yorkshire coast there are Ammonites representing 
geological formations which do not occur on the land; and on the Norfolk and 
Suffolk coasts it has long been known that interesting remains of Pleistocene Mammals 
can be recovered by the trawlers from the sea-bed on the Dogger Bank. Some fresh- 
water mussels once found at the bottom of the sea at the Atlantic end of the English 
Channel seem to show that there are river-deposits in this Channel from which 
valuable specimens may also be dredged at any time. 
Finally, newly ploughed fields after rain should never be neglected for well-_ 
weathered fossils or for stray pebbles and human stone implements. 
In addition to the field observations and collecting, good service can be done at 
home by those who have the time and patience to make preparations of the softer 
sedimentary rocks to show the nature and relative proportions of their several 
constituent particles. After the rock specimens have been disintegrated, the 
particles can be separated into groups by using fluids of different densities, and some 
further separation can then be done laboriously under the microscope. Preparations 
of this kind are needed in large number to determine the possible origin or origins of 
the sediments, thus adding to our knowledge of the land areas and the direction of the 
rivers and currents at the various geological periods. It must also be added that for 
those who are able to arrange more elaborate apparatus, there is still almost unlimited 
scope for making useful microscope-sections of both rocks and fossils. 
The collection of fossils in most parts of this country is now much more difficult 
than formerly. Better facilities for transport and the relatively high cost of building 
in stone, have caused most of the smaller quarries to be closed; while the larger 
quarries have introduced machinery which usually prevents much careful searching. 
Some former industries which led to the discovery of many fossils—such as pyrites- 
gathering on the shores of Kent and Dorset, and phosphate-workings in Hast Anglia 
—have also come to an end. It is thus no longer easy to obtain fine specimens like 
those contained in the great collections of last century’s amateurs which form the 
greater part of the British geological treasure in the British Museum. Many of those 
early amateurs were well-to-do men and women who supplemented their own efforts 
by employing patient and skilled professional collectors who could devote their 
whole attention to the task. Under present changed circumstances, such collectors 
could no longer make a livelihood. 
Posxil-collscting, however, remains just as important as ever for the progress of 
our science, only most of it must be done in a different manner and usually with a 
different object. While nearly perfect specimens are still welcomed whenever they 
can be obtained, the exact localities and formations in which they were found must 
be truly stated, and not falsified to mislead rival collectors as was often the case in 
pioneer days. These fine specimens are no longer the main object of search, but rather 
a multitude of typical fossils of each stratum, whether complete or fragmentary, 
which can be studied intensively from our present standpoint. Fragments are often 
as important as whole specimens, for they may display features which are obscured 
when the fossils are not broken. . Being now convinced of the truth of the dectrine 
of organic evolution, we are anxious to work out as many genealogies as possible 
among the fossils of successive geological periods, and so to discover some general 
principles. This can only be done by attending to a multitude of minute details. 
In most cases alterations in the groups of fossils in successive layers of rock are 
due in large part to the migration of faunas following changes in local conditions. 
We can then only begin to study the evolution of the various animals represented 
after we have collected the evidence from many localities. In any great geological 
formation it is necessary to determine the precise succession of groups of fossils in the 
series of beds in each available section where they occur, so that one succession may 
be compared with another. When this has been done in many sections over a large 
area, it is possible to discover the local gaps in the succession and what would be the 
complete series if all the groups happened to be shown superposed on one another in 
any one spot. The late Mr. 8. S. Buckman most laboriously studied the Lower 
Jurassic formations in this way, tried to discover local gaps, and eventually supposed 
MM 2 
