PRESERVATION ii 
frequently comes across the remains of plants and animals that 
have undergone very little change, and have, as it were, been 
simply sealed up. The state of a fossil depends on several 
circumstances, such as the soil, mud, or other medium in which 
it may happen to be preserved. Again, the newest, or most recent, 
fossils are generally the least altered. We have fossils of all 
ages, and in all states of preservation. As examples of fossils 
very little altered, we may take the case of the wonderful collec- 
tion of bones discovered by Professor Boyd Dawkins in caves in 
various parts of Great Britain. The results of many years of 
research are given in his most interesting book on Cave-Hunting, 
This enthusiastic explorer and geologist has discovered the remains 
of a great many animals, some of which are quite extinct, while 
others are still living in this country. These remains belong to 
a late period, when lions, tigers, cave-bears, wolves, hysenas, and 
reindeer inhabited our country. In some cases the caves were 
the dens of hya3nas, who brought their prey into caverns in 
our limestone rocks, to devour them at their leisure ; for the 
marks of their teeth may yet be seen on the bones. In other 
cases the bones seem to have been washed into the caves by old 
streams that have ceased to run ; but in all cases they are 
fairly fresh, though often stained by iron-rust brought in by 
water that has dissolved iron out of various rocks — for iron is a 
substance met with almost everywhere in nature. Sometimes 
they are buried up in a layer of soil, or “cave-earth,” and at 
other times in a layer of stalagmite — a deposit of carbonate of 
lime gradually formed on the floors of caves by the evaporation 
of water charged with carbonate of lime. 
Air and water are great destroyers of animal and vegetable 
substances from which life has departed. The autumn leaves 
that fall by the wayside soon undergo change, and become at last 
