——— == = - ~~" 
TRANSACTIONS 
OF THE 
ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
I. Zimber: Its Strength, and How to Test [t+ By T. Hupson 
Beare, M.Inst.C.E., Regius Professor of Engineering in the 
University of Edinburgh. 
A very large number of experimental observations on the 
strength and other properties of the various kinds of timber 
which are used by engineers, architects, and builders has been 
published in the proceedings of various technical societies, in 
technical journals, and in text-books. Unfortunately, many of 
these older tests are unreliable, and if the data deduced from 
them are employed in calculations, considerable judgment is 
needed before such data can be adopted with safety. Justifica- 
tion for such a statement is to be found in the following facts :— 
1. In no case, so far as I know, in these older experiments 
was any attempt made to determine the moisture present in 
the timber at the time the test was carried out, and in very 
few cases were data given as to the time of felling, the length 
of time during which the timber had been seasoned, etc.; now 
the amount of sap or moisture present in timber is a very vital 
factor in determining its mechanical properties. 
2. Owing to the fact that the apparatus at the disposal of 
the experimenters was not sufficiently powerful to make any 
other method possible, the tests were mainly made upon very 
small specimens, usually selected with great care on account of 
their freedom from knots and other blemishes; the results are, 
therefore, not really representative of the average quality of 
the particular kind of timber the specimens were supposed to 
represent. 
Tc the late Professor Bauschinger is due the credit of institut- 
ing a really scientific method of carrying out tests of timber, 
1 Lecture delivered before the Dundee Institute of Engineers, November 
17, 1904. 
VOL. XIX. PART I. A 
