Periodical Literature 391 



5o-year beech stand there would be involved 18.3 per cent of 

 area and 18.6 per cent of volume. 



Under severe thinnings in the subdominant, the beneficial ef- 

 fect of which lies in an early beginning, in the middle age the 

 number removal naturally declines, while in the moderate thin- 

 nings it remains more or less even, so that eventually the tw^o 

 come to the same numbers, but the yield from the severe thinnings 

 in volume and value is always larger, since better sizes are in- 

 volved : the severe thinning does not, as has been asserted, swamp 

 the market with inferior material, but on the contrary it furnishes 

 better class material ; only during the transition time from poor 

 practice into the better may a temporary excess of small assort- 

 ments be involved. 



In further discussion of the attitude of practitioners to ex- 

 perimental areas, the author cautions against the mistake of 

 looking at these areas as models : such areas are to find out ef- 

 fects in all gradations in order to find the optimum which is ex- 

 pressed by the sustained value production on a wood capital in 

 most favorable condition as to density of stand and time of pro- 

 duction. 



Forstliche Tagesfragen. Tharandter Forstliches Jahrbuch, 1914, volume 

 65, pp. 351-376. 



At this time, when the establishment of 



Experimentation experiment stations has come into vogue in 



in this country, it is worth while to recall a 



Sihiculture publication, although nearly three years old, 



by Dr. Vater, the well-known soil chemist 



at Tharandt, in which he analyzes the factors of success in silvi- 



cultural experimentation and the causes for the poor success 



the experimenters have so far had. (This in Germany!) 



The first trouble is that experimenters in silviculture, however 

 careful in trying to secure a high degree of reliability, fail mostly 

 to subject their results to a mathematical determination of the 

 average error of their experiments, for which it is necessary to 

 determine those errors which occur even when in a repetition 

 apparently all conditions of the experiment are the same. The 

 errors resulting from the unwilled variations of our actions are 

 found by repeated measurement when an average and the devia- 



