Current Literature. 195 



1. A high degree of steaming is injurious to wood, the injury 

 depending upon quality and condition of the wood and the degree 

 of steaming. For loblolly pine the limit of safety is 30 pounds for 

 4 hours or 6 hours at 20 pounds. 



2. The presence of zinc chlorid does not weaken wood under 

 static loads, but appears to make it brittle to impact. 



3. Creosote of itself does not weaken the wood, but retards the 

 seasoning. 



The circular comprises 31 pages, 13 tables and 2 figures. The in- 

 formation given is not only new, but of great practical value to en- 

 gineers dealing with treated wood. It will doubtless give an impetus 

 to the use of proper preservation treatments. 



H. D. T. 



Sugar Pine and Western Yellow Pine in California, by Albert TV. 



Cooper. Bulletin No. 69, U. S. Forest Service, Washington, 



I9O6. 

 This bulletin reports the results of a study by the U. S. Forest 

 Service in cooperation with the State of California. The author 

 has given an excellent silvical description of the two species, includ- 

 ing their distribution in California, and a full description of the 

 forest types which they form. Many points of interest are brought 

 out in this description, for example, it is stated that sugar pine is 

 the most intolerant conifer in the Sierras, thus placing it below yel- 

 low pine and Douglas spruce. The scale of tolerance is: incense 

 cendar, white fir, Douglas spruce, yellow pine, sugar pine. Such a 

 scale is, of course, somewhat misleading because the requirements 

 for light in different periods of the life of the trees, and it is very 

 difficult to distinguish between the demands for light and demands 

 for moisture. Thus Mr. Cooper states that sugar pine demands a 

 certain amount of shade in early youth. This, taken together with 

 other statements in the bulletin, would indicate that young sugar 

 pines are sensitive to drying influences in youth. The silvical de- 

 scription of the trees is unusually complete, the author giving not 

 only the scale of tolerance of the various species, but also comparing 

 their capacity to bear shade and to resist fire. 



One of the interesting statements made is that the Sierra forests 

 are for the most part composed of even-aged stands. In view of 

 this fact it is unfortunate that the stand tables were made to show 

 only the relative occurrence of trees of different sizes. Readers 

 would like to know olso the character of the forests with reference 



