PKKIODICAI, r.ii'KRA'i'UKl-; 939 



wliat over 15,000 acres. Every fortieth stem in each diameter-class was 

 taken as a sample tree and its contents and increment determined ac- 

 cording to Tor Jonson's method on standing trees. In this way 32,746 

 sample trees, distributed over the whole country, were more especially 

 investigated. The surve\' was made with cojnpass and steel tape on the 

 basis of good maps. 



We may state briefly the results. The growing stock was found to 

 be 94.5 ± 1.45 per cent cubic feet per acre and the increment 3.54 per 

 cent. It was found that increment and utilization compensated them- 

 selves except for tiie considerable quantity of wood which decays and 

 gets lost otherwise before the stems have grown to use; so that, after 

 all, utilization exceeds increment. The characteristic of the forest con- 

 ditions of Vaermland is found in the large representation of younger 

 age-classes and siuall diameter-classes, due to the extensive cutting in 

 the middle and latter part of the last century. The young stands are 

 mostly in good condition. 



The most interesting part of the statement is the method pursued to 

 investigate the degree of accuracy of the result, for which purpose a 

 ]irobability calculation was employed. To a]^ply this calculation the 

 strips were systematically divided into pieces 1 km. in length, so that 

 each piece represented i hectare (2.5 acres). To give these sample 

 areas .symmetrical arrangement, there was laid off from the intersec- 

 tion of a strip, going through the middle of the territory and the middle 

 meridian of the province, a line perpendicular to the strip lines from 

 which intersections the km. -long j)ieces were measured. These were 

 designated by strip and piece numlx-r. In ap])lying the ])robability cal- 

 culation these areas were combined into groups, the first grou]) being 

 composed of the areas, numbered i, 11, 21, 31. etc., the second series 

 nuiubered 2. 12, 22, 7^2, etc. In this way the whole estimate was 

 divided into ten inde])en(lent partial areas, each of which rei)resented 

 one-tenth of the total estimated area, and on this basis the average 

 error of the result was calculakd. It apjicarcd that tlio distribution of 

 areas follows right closely the laws of probability, making a comparison 

 of the surve\' witli the actual areas given on a first-class map of the 

 territory show as follows: 



.\rca AviTiiKi- 



, — -*■ ^ calciil.itol Ai-tual 



Hectares ,\cres error error 



Per iciil Per cent 



I'icUi J4t).5-'<) 616,314.40 ± I . J7 — 1 .42 



Waters iKo.ojj 444,654.34 ±3.f>K — 1.41 



Forest soil i,4<)<),3iX 3.703.340.16 'Kmi Fo.3i 



The actual nrors, tluTcfoir. lie within thrci' times the avcraire error. 



