218 Canadian Record of Science. 



around the base of the tree, and regular layers of peat 

 moss and forest vegetation had accumulated above the 

 roots during the long period of its growth. 



During this period of four hundred years it would 

 appear that the bog added only six inches to its depth. 

 As far down as the charcoal layer there is no great differ- 

 ence in the nature of the bog deposit ; sometimes an extra 

 amount of forest mould shows that the trees which grew 

 along the borders of the bog were able to throw out colo- 

 nies into the open sphagnous area ; at others a return of 

 a moister climate reversed the conditions, and the bog 

 encroached on the forest ; but assuming that the growth 

 was comparatively uniform, twelve hundred years would 

 have elapsed from the time when the charcoal layer was 

 deposited until the seed of this cedar sprouted in the moss 

 of the bog. 



But in estimating the age of the charcoal layer, other 

 factors are to be considered : one of these is the condensa- 

 tion of the peat in the lower layers by the weight of the 

 superincumbent mass of vegetable matter. To test this, a 

 sample of the peat above the roots of the cedar tree was 

 weighed and compared with that of the peat a foot down 

 from the surface ; the latter was found to be a third hea- 

 vier, showing a considerable condensation of the mass ; at 

 a lower level the weight was still greater. Allowing for 

 the reduction of bulk from this cause in the lower layers, 

 I think it may be assumed that 2,000 years have elapsed 

 since the charcoal layer was deposited, and therefore since 

 the occurrence of the forest conflagration of which it is a 

 witness. 



