Periodical Literature. 97 



worth about $13.00 per mile and weighs 58 pounds per mile. If 

 reeled up in the fall it has a life of 6 to 7 years while if left over 

 winter it will last about 4 or 5 years. 



These wires are recommended for temporary patrol or look- 

 out points and for connection with two or three day camps in 

 fire season. 



Timberman, 191 1. 



MENSURATION, FINANCE AND MANAGEMENT. 



The forester is continually dealing with 



Averaging. average figures; he should therefore know 



the principles of averaging, for this is not 



always as simple as it appears, the volume per cent formula 



400 



— -7- applied to stands being a case in point. 



Dr. v. Lorenz develops with considerable mathematical ap- 

 paratus the proper methods of averaging diameters, cross-section 

 areas, comparisons of diameter and area averages, and of stand 

 volumes after Hartig's sample tree method. 



In the last case he shows that not less than five more or less 

 rational formulae can be developed to average the sample trees, 

 giving, of course, five diflferent results. 



We cannot afford to reprint the 71 formulze and their develop- 

 ment, which are given to show which averages are correct or the 

 conditions under which different averages are correct. But those 

 who are in the position of teaching forest mensuration should con- 

 sult the original source. 



Zur Bildimg von Mitllezahlcn. Centralblatt fiir das gesammte Forst- 

 wesen. December, 1911. Pp. 541-558. 



In the continuation of Tafel's discussion of 



Forest the principles of loaning on forest property. 



Loans. (briefed in F. O. vol. IX, p. 638) a few 



of the incidental data are of interest. For 



instance, the statement that in spruce the value increment per 



cent (which includes volume and price per unit measure) on site 



I has already sunk to 3.8% in the 50th year, on site II to 3.9% 



in the 60th year, on site III to the same rate in the 70th year; on 



site IV, it is 2)-^% in the 80th year, on site V only 2.1% in the 



7 



