i8 GEOLOGY OF THE ISLE OF WIGHT 



chains of lofty mountains far away, from which the head 

 waters of the river flowed. Near its mouth the river 

 broke up into many streams, separated by marsh land ; 

 while inside the sand banks of the sea shore would be 

 large lagoons as in the Nile delta at the present day. 

 In these waters lived the shellfish whose shells we are 

 finding. And flowing through great forests the river carried 

 down with it logs of wood and whole trees, and left them 

 stuck in the mud near its mouths for us to find to-day. 



What kind of trees grew in the country the river came 

 from ? Well, there were no oaks or beeches, no flowering 

 chestnuts or apples or mays. But there were great 

 forests of coniferous trees ; that is trees like our pines 

 and firs, cedars and yews, and araucarias ; and there were 

 cycads a very different kind of tree, but also bearing 

 cones which you may see in a greenhouse in botanical 

 gardens. They have usually a short trunk, sometimes 

 nearly hemispherical, with leaves like the long leaves of a 

 date palm. They are sometimes called sago trees, for 

 the trunk has a large pith, which, like some palms, gives 

 us sago. Stems of cycads, covered with diamond-shaped 

 scars, where the leaf stalks have dropped off, are found 

 in the Wealden deposits. Most of the wood we find is 

 black and brittle. Some, however, is hard as stone, where 

 the actual substance of the wood has been replaced by 

 silica, preserving beautifully the structure of the wood. 

 Specially noteworthy are fragments of a tree called 

 Endogenites (or Tempskya) erosa, because it was at first 

 supposed to belong to the endogens, the class to which 

 the palm bamboo belong ; it is now considered to be 

 a tree-fern. Many specimens of this wood are remark- 

 ably beautiful, when polished, or in their natural con- 

 dition. Here, by the way, it may be well to explain how 

 we name animals and plants scientifically. We have 

 English names only for the commoner varieties. So we 

 have to invent names for the greater number of living and 



