8 ANIMALS OF THE PAST 



of weathering. Not so the organic shell ; this eventually 

 would decay away, and so leave the filling or kernel of 

 chalcedony and lime. 1 



" Fossil leaves" are nothing but fine casts, made in 

 natural moulds, and all have seen the first stages in their 

 formation as they watched the leaves sailing to the 

 ground to be covered by mud or sand at the next rain, 

 or dropping into the water, where sooner or later they 

 sink, as we may see them at the bottom of any quiet 

 woodland spring. 



Impressions of leaves are among the early examples of 

 color-printing, for they are frequently of a darker, 

 or even different, tint from that of the surrounding rock, 

 this being caused by the carbonization of vegetable 

 matter or to its action on iron that may have been 

 present in the soil or water. Besides complete miner- 

 alization, or petrifaction, there are numerous cases of 

 incomplete or semi-fossilization, where modern objects, 

 still retaining their phosphate of lime and some animal 

 matter even, are found buried in rock. This takes place 

 when water containing carbonate of lime, silica, or 

 sometimes iron, flows over beds of sand, cementing the 

 grains into solid but not dense rock, and at the same 

 time penetrating and uniting with it such things as 

 chance to be buried. In this way was formed the 

 " fossil man" of Guadeloupe, West Indies, a skeleton of 

 a modern Carib lying in recent concretionary limestone, 

 together with shells of existing species and fragments 

 of pottery . In a similar way, too, human remains in 

 parts of Florida have, through the infiltration of water 

 charged with iron, become partially converted into 



'Right here is the weak spot in Professor H.-nbour's explanation, and 

 an illustration of our lack of knowledge. For it is difficult to see why the 

 more enduring husk should not have become mineralized equally with 

 the cavity within. 



