i6o 



FORESTRY AND IRRIGATION. 



April, 



sar}^ for me, in attending to the details 

 of the lumbering business in which I was 

 engaged, to travel through the Adiron- 

 dack forests a great deal of the time, 

 more especially in winter, and I have 

 often been startled by the sharp, whip- 

 like crack of a tree within a few feet of 

 me. 



Actuated by a desire to know just 

 what caused the marked difference in 

 sound when frost was going in or com- 

 ing out of the tree, and what effect the 

 sudden changes had on the timber, I 

 have for a number of years been study- 



FIG. I. SHOWS EFFECT OF A CONTRACTION 

 FROST CHECK UPON SPRUCK. 



ing this subject in different localities 

 and at different elevations. As a result 

 I have come to the conclusion that the 

 greater part of the so-called wind shake 

 in timber is in reality primarily caused 

 by frost checks. 



The so-called wind shake is much less 

 noticeable in warm climates, there be- 

 ing but a small amount when compared 

 with those localities where the timber 

 is subject to sudden extremes of heat 

 and cold. Neither are frost checks 



or wind shakes as plentiful, nor their 

 effect on timber as damaging, in the 

 country farther north, where it is at 

 times extremely cold, but where the 

 changes from one extreme of temper- 

 ature to the other are more gradual, as 

 they are in these degrees of latitude 

 where there are lesser extremes of heat 

 or cold, but with much more rapid tran- 

 sitions from one extreme to the other. 

 These facts are a very strong argument 

 in favor of the theory that the wind 

 shake is primarily a result of frost. 



Checks caused by the frost when go- 

 ing into a tree have almost invariably 

 been found to extend in a perpendicular 

 direction up and down the trunk, in- 

 variably following the grain of the wood 

 as it would split with an axe. In look- 

 ing for the reason for this, it becomes 

 apparent that these checks in the wood 

 are caused by the sudden contraction 

 of the outside of the tree, brought about 

 by intense cold. 



The long, straight gum seams, es- 

 pecially noticeable in spruce timber, 

 often found above the middle height of 

 the tree, are almost invariably caused 

 by contraction (Fig. i). Such checks 

 once opened, are afterward kept from 

 closing and becoming solidified b}' the 

 action of the wind on the top, in work- 

 ing the tree to and fro ; also by ex- 

 tremes of high and low temperatures 

 quickly following each other. 



In succeeding changes from a high 

 temperature, the check being the weak- 

 est point in the tree trunk's surface, is 

 the first to give way under the influence 

 of contraction. From the check thus 

 made gum exudes and is pressed out 

 to the surface of the tree by the con- 

 traction and expansion, or opening and 

 closing of the seams. This gum forms 

 along the seams in globules or lumps, 

 which are hardened by exposure. 



The action of frost when going in and 

 out is almost exactly opposite in its 

 effect on trees. When frost is going 

 into a tree the outside rim or surface 

 commences to contract, and if there is a 

 sudden change from a high temperature 

 to an extremely low one, the outside 

 layer contracts more rapidly than the 

 inside layers of timber for the reason 

 that the outside is directly exposed to 



