26 FOREST RENEWAL. 



entirely different form from forms now existing. In fact the eartti 

 has probably passed the point where life could originate at all. The 

 first conditions under which vegetation occurred were doubtless such 

 as to have proved fatal to later and especially to present forms. It is 

 not only the extraordinary tidal action and storm power but also a 

 probable difference in the chemical composition of the atmosphere that 

 would have made primitive conditions fatal to present forms. Tne vio- 

 lent and frequent upheavals and subsidences that the location of the 

 coal strata demonstrate to have taken place during the carboniferous 

 epoch indicate a rapid growing and dense forest and one taking pos- 

 session of new soil easily. These coal forests were of a different char- 

 acter of growth from any forest now existing. They were probably 

 produced on alluvial deltas subject to elevation and submergence and 

 to a coincident heavy deposit of detritus during the periods of subsi- 

 dence. Thus the fern like forests grew, were destroyed, were covered 

 with rock-making detritus, were compressed and carbonized and then 

 the delta elevated above water again produced forests; and again going 

 through such histories we find veins of coal alternating with veins of 

 rock one above another. We can then feel confident from the rock rec- 

 ords of the coal forests that a forest destroyed may be renewed by 

 natural means. In fact we know that in most forested districts a mere 

 absence of human action will insure a new forest growth. Perhaps 

 this growth will not be as valuable as the primeval forests but for its 

 effects in conserving the water holding power of water-sheds there 

 would be little if any difference. Man by aiding nature can increase 

 the certainty and rapidity of reforestation. He can also secure a more 

 valuable crop and determine what the forest shall be within limits. 



A FOREST DESTROYED MAY NOT ADMiT OF RENEWAL. 



We noted the presumption that conditions in the world were chang- 

 ing. However slow these changes are we cannot escape from the conclu- 

 sion that changes are going on. There comes a time then when condi- 

 tions may be so close to the limit of permitting forest life that a very 

 slight change may determine the issue. The change may be so slight 

 that man or animals may make it. That a time does come in changes 

 of climate and perhaps in other conditions when a forest destroyed can- 

 not renew Itself nor be replaced by any growth is subject to positive 

 demonstration. I have visited two petrified forests in which the stone 

 trees lay thick on the desolate desert valleys. These petrified trees 



