1833,] 333 (Day. 
Z% was the last introduced of the letters of the Roman alphabet. * * * 
It crept into English during the fifteenth century from the French, and in 
use is now pretty nearly restricted to foreign loan-words * * * ¢edilla 
means little zed: zediglia is the diminutive for zetécula.”” p. 138. 
The Microscopic. Hxamination of Timber with regard to its Strength. A 
Jontribution from the Bi Kk. Price Botanical Laboratory of the University 
of Pennsylwania. By Frank M. Day. 
(Read before the American Philosophical Society, December 21, 1883.) 
The valuable paper of Dr. J. T. Rothrock upon “Some Microscopic 
Distinctions between Good and Bad Timber of the Same Species,’’ re- 
cently read before the American Philosophical Society, has opened a broad 
field for original investigation. The question there suggested as to the 
possibility of approximately determining the strength of timber by micro- 
scopic examination (involving as it does the question of the ‘differences 
in the strength of wood due to the molecular differences in the structure 
of the fibre ’’) is one that can be answered only after the most extended 
and carefully conducted investigation. 
As long as we confine ourselves to the examination of various specimens 
of the same species the task of distinguishing the good pieces from the 
bad, and of roughly predicting the relative strains which they will resist, 
is comparatively easy.* 
Plate I showing transverse sections of two pieces of Rock Elm (Ulmus 
racemosa Thomas), furnishes illustrations of the general differences be- 
tween good and bad wood of the same species. The upper figure is a sec- 
tion of the wood used by a well-known firm in their highest grade. of 
hubs ; the lower isa section of wood which they declare to be practically 
worthless, It is evident froma glance at these drawings that the good differs 
from the bad, in 1st, The much smaller area occupied by ducts; 2d, The 
smaller bore and consequently thicker walls of the woody fibres ; 3d, The 
more compact arrange vent of the woody fibres, giving them a polygonal 
rather than a circular outline; 4th, The much greater annual growth, 
These are the elements which it is but reasonable to suppose would give 
strength to the wood, They are further those which are found to do so 
in the great majority of cases. 
The strength of the cellulose of which the wood is composed, is, in va- 
rious species and under various conditions, by no means the same. For 
example, Buttonwood (Platanus occidentalus L.) rapidly loses the greater 
part of its strength, by a natural process which the woodsmen call ‘‘doat- 
ing,’’ the only indication of which isa bleaching of the tissues. Hence 
any statements as to the strength of timber, made from an examination of 
the structure alone are open to question. 
* This it will be urged can be done by the practical eye without the aid of the 
microscope, but it must be remembered that the entire investigation of the 
Subject is, at its present stage, of theoretical rather than practical interest, 
