RECENT INVESTIGATIONS IN REGARD TO QUALITY OF TIMBER. 281 
The specific gravity was determined in Friedrich’s Xylometer, an 
instrument which gives readings to 1 c.cm. (= '; cub. in.). Before 
immersion in the xylometer, the dry wood was first coated with 
linseed oil, the object being to prevent absorption of water and 
consequent swelling, which would, of course, have interfered with 
the accuracy of the determination. Resistance to crushing was 
determined by Pohlmeyer’s 100-ton testing machine, or, if this 
failed to crush the specimen, Hoppe’s 500-ton machine was 
brought into requisition. Before testing, the wood was periodi- 
cally weighed, and when two consecutive weighings gave the 
same figure, the specimen was said to be “air-dry,” and in the 
desired condition for investigation. As further indicating the 
extensive character of the inquiry, it may be mentioned that 
the Scotch fir alone necessitated 4856 volumetric determina- 
tions, 2428 weighings, and 1247 pressure determinations, the 
tabulating of which gave employment to two calculators for 
six months, 
The specific gravity of water is taken as 1, so that the specific 
gravity of timber, being generally less than that of water, is 
generally a fraction of 1. The specific gravity of a specimen of 
timber being given, one can at once calculate the weight of a 
cubic foot, by multiplying the weight of a cubic foot of water 
(62:5 lbs.) by the specific gravity of the timber in question, Thus 
the weight of a cubic foot of pine, whose specific gravity is 6, is 
62°5 x 6=374 lbs. The resistance to crushing is stated by Prof. 
Schwappach in terms of a kilogram per square centimetre. I 
have, however, converted these terms into “pounds per square 
inch,” by taking 1 kilo. = 2:2 lbs., and 1 square inch = 6:45 square 
centimetres, 
The following is a short summary of the main conclusions that 
Prof. Schwappach and his colleagues have arrived at, 
I. Wits THe Scotcu Fir. 
The sp. gr. depends on (a) the quality of the situation ; (d) its 
geographical position; (c) the height from the ground of the 
point from which the specimen is taken ; (d) the age of the tree ; 
and (e) the relative development of the spring and autumn 
wood. 
The sp. gr. decreases more or less steadily as a tree is followed 
from the ground upwards, but it shows a tendency to increase 
VOL, XV, PART III, 2A 
