io EXTINCT MONSTERS. 



have undergone very little change, and have, as it were, been 

 simply sealed up. The state of a fossil depends on several cir- 

 cumstances, 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 collection 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. Thio 

 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, hyaenas, and 

 reindeer inhabited our country. In some cases the caves were 

 the dens of hyaenas, 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 

 separated or resolved into their original elements. In the same way 

 when any wild animal, such as a bird or rabbit, dies in an exposed 

 place, its flesh decays under the influence of rain and wind, so that 

 before long nothing but dry bones is left, Hamlet's wish that 



