HANDBOOK OF FOSSILS. 69 



HOW TO USE YOUR IMPLEMENTS. 



We will suppose by way of illustration that near us flows a 

 river, on the rising ground above which is a pit that we propose 

 to visit for the purpose of putting our apparatus into practical 

 operation. When we have reached the floor of the pit, and 

 stand looking up at the section before us, we are at first 

 rather puzzled as to what the beds, which we see before us, 

 are ; for as the pit has not been worked for some time, its 

 sides are partially overgrown with grass, and in places bits 

 and pieces of the upper beds have fallen down and form a 

 heap beneath which the lower ones lie buried. We must there- 

 fore make our way to those spots where the beds are left clear, 

 and find out, if possible, what they are. By climbing up one of 

 the heaps of fallen earth (talus] we reach the top, where, first of 

 all, under the roots of the grass and shrubs, we find the mould in 

 which these grow, and which is formed of the broken up (disinte- 

 grated] rocks forming the still higher ground above, and which 

 the rains, frosts and snows, aided afterwards by the earthworms, 

 have converted into mould. This, geologically speaking, is 

 called surface soil, and is here about two feet deep. Just below 

 it we find a layer of coarse gravel ; the pebbles of which this is 

 composed are of all sorts, sizes, and shapes, and are stained a 

 deep brown by oxide of iron. Most of them are flints, and by 

 diligent search you may find casts and impressions in these of 

 sponges, shells, spines of sea urchins, etc. Flints, whether from 

 gravel or their parent rock the chalk, are easiest broken by a 

 light smart tap of the hammer, though when it is desired to 

 shape them for the cabinet a soft iron hammer should be used, 

 and the piece to be shaped placed on a soft pad on the knee, 

 for when struck with a steel hammer flints splinter in all 

 directions, and often through the very portion you most desire 

 to preserve. In one spot we find a mass of sand included in 

 the gravel ; this mass is thickest in the middle, and tapers 

 away towards each end, its total length being about fifty feet. 

 Could we see the whole mass, we should probably find it to 

 be a patch lying on the gravel and thinning out all around its 

 edges ; in other words it would be shaped like a lens "lenticu- 

 lar " as geologists term it. When we examine this mass more 

 closely, we find that the layers of sand do not run parallel with 

 the bed, but are inclined in different directions, sometimes lying 

 one way, sometimes another. This false bedding is due to the 

 sand having been thrown down in waters agitated by strong 

 currents that swept over the spot, now in one direction and now 



