December 14, 1906.] 



SCIENCE. 



761 



one contemplates the long time which is in- 

 volved, the many changes to which the crop 

 is subjected during that time, varying its rate 

 of growth from period to period, and its 

 character, which the forester must be able to 

 foresee. Finally, where finances are involved, 

 market conditions must also be predicted: the 

 forester must be a seer! 



As in the factory, cost of output and sale 

 value of product are compared, so in forestry 

 the cost of producing wood and its eventual 

 sale value need to be placed in relation. But, 

 before a financial calculation can be made, 

 we must be able to measure the product itself, 

 and the methods that are employed to measure 

 the volume of trees or parts of trees, of stands, 

 forests, and of their increments from period 

 to period are comprised under the name of 

 forest mensuration. 



It was quite natural that the first American 

 professional text-book of forestry, worthy of 

 the name, should occupy itself with this 

 branch of the subject, which is to a large 

 degree basic of all other branches. Dealing 

 mainly with mathematical questions, it was 

 possible to bodily transfer the European 

 knowledge and practise, ready for our use. 



The art of forest mensuration, as all other 

 branches of forestry, has naturally been main- 

 ly developed in Germany, and as regards 

 m.ethods of procedure in the measurement, 

 especially of standing timber and of incre- 

 ment, the author could add litttle to the con- 

 tents of the latest German text-books. But 

 in the matter of measuring felled timber, es- 

 pecially logs, the American method of em- 

 ploying the board-foot or some similar stand- 

 ard gave opportunity to add the matter 

 contained in chapters II. to V. on log rules 

 and scaling of logs, which would naturally 

 not be found in European literature, the neces- 

 sity for which we consider, however, a na- 

 tional misfortune. 



It is unfortunate that we are doomed to 

 remain in the backwoods as regards our units 

 of measurement. If it is a pity that we have 

 not yet adopted the metric system, it is almost 

 a sin that we persist in continuing the use of 

 the absurd log scales, and we regret that Pro- 

 fessor Graves has not used the opportunity 



of inveighing more severely against this in- 

 cubus. 



There are not less than forty-five standards 

 or units of measurement for logs employed in 

 the United States, all varying in the board- 

 foot contents they give for logs of the same 

 cubical contents. It is a matter of experi- 

 ence that the results at the mill invariably 

 belie the log scale. Professor Graves has 

 treated this subject most fully and with an 

 elaboration worthy of a better cause, admit- 

 ting at the same time that ' the cubic foot 

 will unquestionably be used more and more, 

 as the value of timber increases and eventu- 

 ally replace the present rough unit, the board- 

 foot.' 



The other parts of the book are treated with 

 similar clearness and elaboration, and the 

 whole must be recognized as much a standard 

 work — the first in the English language on 

 the subject — as any of the best German text- 

 books. Indeed, this book is in some respects 

 an improvement by the addition of results of 

 measurements in tables, which are usually not 

 given in such text-books. The methods of 

 estimating standing timber are also more 

 elaborated than in European literature. 



We welcome this contribution to profes- 

 sional forestry literature as distinctly an ad- 

 vance to our forestry movement. 



B. E. Fernow. 



THE NUMBER OF KNOWN FERNS. 



Few persons not familiar with fern litera- 

 ture can begin to appreciate the scattered 

 nature of the information that must be 

 gleaned and sifted in the systematic study of 

 the ferns of any region outside of temperate 

 North America and Europe. The last sum- 

 mary of the ferns of the world was published 

 a generation ago (1874) and proved a most 

 useful work, notwithstanding two facts: (1) 

 that its conservative authors, throwing geo- 

 graphic distribution to the winds, often in- 

 cluded from two to twenty species under the 

 single name of one of their so-called species 

 of general distribution; and (2) that the use 

 of the Kew method of citation for the author 

 of the species made it practically impossible 

 to trace a given species to its original descrip- 



