290 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
The shrinkage rose and fell with the sp. gr., being 15:2 % 
where the sp. gr. was °705, and 14:4 % where the sp. gr. was 
‘632 (see above). For general use a shrinkage of 15 7/ in beech 
timber may be taken as a sufficient approximation. 
Resistance to pressure was found to be at a minimum at about 
two-thirds of the height of the tree, and at a maximum about 
4 metres from the ground. In the case of this tree the points 
of maximum pressure-resistance and maximum sp. gr. do not 
quite coincide, though the variation is only insignificant. Prof. 
Schwappach says, ‘From the figures before us it would appear 
to be a matter of indifference, for practical purposes, which part 
of a beech tree is selected to furnish a beam of timber.” 
Resistance to pressure, however, varies much in trees of 
different ages, being at its maximum (about 8456 lbs, per sq. in.) 
in trees 80-85 years old, and at its minimum in trees of an age 
of 200-220 years (about 6610 lbs. per sq. in.). 
The quality of the locality and the latitude of the situation 
were found to have but little influence on the strength of beech 
timber. 
The limits of variation in the sp. gr. of beech timber were 
found to be :— 
(a) For definite periods of growth, . tao BGM Oa. 
(6) For whole sections, ‘ ; . 749 and °562. 
As regards resistance to pressure, the limits were—a maximum 
of 12,713 lbs., and a minimum of 4825 lbs, per sq. in. 
For well-grown trees the following averages may be taken :— 
Sp. gr. = ‘670. 
Resistance to pressure = 7660 lbs, per sq. in. 
One of the most satisfactory features of these investigations of 
Prof. Schwappach’s is the closeness with which the results agree 
with those obtained by other workers, notably Prof. Robert 
Hartig.! The latter confined himself to determining specific 
gravities, but Schwappach’s work shows that what holds true for 
this physical property will generally apply to pressure-resistance. 
This technical property of timber is but one of many, but it is 
the one that may be relied upon to give the most accurate results, 
If ordinary care be exercised in selecting the cubes to be operated 
' For some of Hartig’s results, see Zvans. High. and Ag. Soc,, 1890, p. 26. 
