ON COLLECTING MICROSCOPIC ORGANISMS, ETC. 131 
natural sections should be searched for fossils weathering out; and 
more particularly the talus at the foot contains fossils washed out 
from the rocks above. 
Stone fences round fields, etc., often reveal fossils much more 
distinctly than rocks freshly quarried ; but care is required to extract 
the fossils without damaging the fences. 
Specimens of prominent beds of limestone and chert should be 
obtained for examination by microscopic sections, even if no fossils 
can be seen by the eye alone. Small cubes 1 or 2 inches across will 
serve for this purpose, but the locality requires to be carefully noted. 
Specimens of dark cherts, or cherty nodules, should be more particu- 
larly obtained, as they usually contain Radiolaria in better condition 
for showing their structures than transparent cherts. Small cubes of 
the softer kinds of calcareous rocks, such as the various varieties 
of beds of chalk and cubes of siliceous shales and marls, should be 
collected for the preparation of microscopic sections or for subsequent 
levigation. 
The beds of streams cutting through rocky or shaly banks should 
be searched when the water is low in summer and autumn, for fossils 
will often be found in layers of sand and gravel which have been 
naturally washed out of the rocky beds on the banks ; also if hard 
beds of limestone form the floor of the stream, these will be found to 
have fossils standing out in relief, owing to the natural action of 
streams. 
Beds of fissile shale should be split open with the hammer and 
chisel or a broad-bladed thin knife, and their surfaces searched for 
Graptolites, Trilobites, or other Crustacea, small dark annelid jaws, 
Polyzoa, Conodonts, etc. Such forms in shale require careful pack- 
ing, otherwise they soon get defaced during transport. 
