CURRENT LITERATURE. 



Massatabellar for Trdduppskattning. By Tor Jonson. Stock- 

 holm, Sweden. 191 1. Pp. 64, 8°. 



Mr. Tor Jonson, Forest Engineer and Associate Professor at 

 the Royal Forest Institute of Stockholm, Sweden, has after many 

 years of investigation and study published a volume table for the 

 Swedish conifers on a new basis. This table has been very fav- 

 orably received in Europe, and it would be advisable to give the 

 table a test in Canada and the northeastern United States. 



The tables give the contents of the whole stem in cubic meter, 

 arranged in twelve form classes up to 70 cm. 



On p. 62 is a table giving d.b.h. form factors for different 

 heights and form classes. With the help of this table the vol- 

 ume of trees of larger dimensions than given in the table, may 

 very easily be computed- 



Mr. Jonson bases his investigations to a large extent on 

 Schiffel's and Metzger's theories, but does not wholly agree with 

 Messrs. Schiffel, Maass and Tkatchenko, for he measures the 

 "upper diameter" at the middle of the portion of the stem that 

 lies above breast height instead of at the middle of the total height 

 of the tree. This, Jonson thinks is more correct. 



For instance ; in classifying two conical trees ten and thirty 

 meters high above stump, the diameter at the middle height of the 

 trees will be compared with the d.b.h. at one tenth of the height 

 of the short tree and with the d.b.h at 1/30 of the height of the 

 taller tree (breast height 1.3 meter, stump height 0.3 meters.) 

 This brings the ten meter tree into "form class" 0.56 but the 

 thirty meter into "form class" 0.52, this, though both trees have 

 the same (conical) form. On a tree 2.6 meters high, both mea- 

 surements will be taken at 1.3 m. which gives us form quotient i, 

 or cylindrical form, while the tree may really have any form at 

 all without this form quotient being changed. Consequently, 

 trees of different heights must have different form to get into 

 the same form class, which Mr. Jonson considers illogical. These 

 and other inconsistencies disappear almost entirely, Jonson says, 

 if the upper diameter is measured at the middle of the portion of 

 the stem lying above breast height, trees of the same form will 



