150 Forestry Quarterly. 



ures obtained from the Meteorological Station at North Bay 

 indicate an annual precipitation of 30 inches, of which 12.5 inches 

 falls in the tetrahore or four growing months. The mean monthly 

 temperature of the tetrahore averages 60° F., the extremes lying 

 at a minimum of 4° F. in May and a maximum of 96° F. in July. 

 The minimum winter temperature falls to — 45° F. 



In the classification of the forest growth three natural types 

 were distinguished. This separation was based on physiography, 

 which forms a more permanent basis than the nature of the tree 

 growth which is often transient. The types were designated as 

 Ridge Type; Swamp Type; Sand Plain Type. 



The Ridge Type. 



This, in the area under investigation, is the most extensive for- 

 mation and comprises the bulk of the region- The low broad 

 ridges are covered with a thin sand. The growth is stunted and 

 open, the trees finding a foothold mainly in the crevices of the 

 rocks. The three prominent associations which appear are: 



1. Jack Pine-Red Pine-White Pine. This association comes in 

 mainly on the better situations where the soil on the ridge tops 

 has deepened. It forms a transition to the better sites. 



2. Pure Jack Pine. The Jack Pine occurs on the most exposed 

 and rocky situations where the soil is very thin and often lacking 

 save in the crevices and fissures. 



3. Jack Pine-White Pine-Red Oak. On many of the exposures 

 scrubby oak enters in the composition but the Jack Pine is here 

 also the prominent tree. 



The Swamp Type. 



The deep water deposits of heavy clay occurring in patches of 

 varying extent are the cause of this formation. These clays lying 

 at the lower levels are poorly drained and the small creeks which 

 often meander through them are sluggish. The two associations 

 which were noted are: i. Cedar-Fir-Yellow Birch; 2. Black Ash- 

 Elm- The former is the more widespread, the latter being com- 

 paratively restricted. 



The Sand Plain Type. 



Sand Plains are not numerous in this district but where they 

 occur they support the best timber. They appear to form an 



