TIMBER: ITS STRENGTH, AND HOW TO TEST IT. II 
of the sap-wood and four tests of the heart-wood, and they 
include both summer-felled and winter-felled specimens. 
Comparison of Strength of Heart-Wood and Sap- Wood in Tension, 
and of Summer and Winter Felling. 
Tenacity in lbs. per square inch. 
Summer felled. Winter felled. 
Kind of Wood. | 
Sap-Wood. | Heart-Wood.| Sap-Wood. | Heart-Wood.) 
Scots Pine, ‘ : : 14,940 3,270 10,660 4,120 
Norway Spruce, : : 13,790 4,413 17,630 4,905 
COMPRESSION TESTS. 
It is a much easier matter to carry out crushing or compressive 
tests of timber, that is, it is much easier to make our specimens, 
and, as a rule, the results obtained are much more concordant 
among themselves. I shall deal here with only the more modern 
results, in which records have been kept of the moisture condi- 
tions at the time of the tests. 
As a result of his investigation, Bauschinger was of opinion 
that when the point which it was desired to elucidate was the 
average quality of any given sample of timber, then compression 
tests were the best. For example, if it was desired to investigate 
for a particular kind of wood, say Scots pine, the influence of the 
time of felling upon the mechanical strength, then it could best 
be carried out by a series of compressive tests. Bauschinger’s 
plan was to cut a disc out of each end, and from the centre of 
each log, then to slice these discs into four sections, and from 
each of these sections to trim out a square prism with its length 
about one and a half times its cross sectional dimension. 
Further, he decided that these specimens (twelve of them) should 
then be brought to a state of dryness such that the moisture was 
about 15 per cent., the density being determined by careful 
weighing and measurement. In his investigation into pine 
wood, Bauschinger found that the strength of short columns of 
this nature varied directly as the density of the wood. 
