Day.] 334. [Dee, 21, 
We are, however, able to leave this uncertain element out of consider- 
ation when we turn our attention to the following experiments upon the 
transverse strength of the coniferous woods, the results of which point to 
an almost identical value for the strength element of the cellulose in the 
several pieces tested. Each piece was exactly one-and-a-half inches 
Square by two feet nine inches long, and rested upon rounded edges at a 
distance of two feet six inches apart. The pressure was gradually applied 
at a point half way between the supports, and the deflection was taken at 
each hundred pounds. 
Plate IL shows, side by side, transverse sections of three pieces thus 
tested, The detail of the experiments are exhibited in the following table : 
a) [83-2 aT. 
‘ 8 4 Des eel o 1A. 
Hs Efe | BEE Res 
fal n | O¢ gn lee yim 4B 
bie NAME OF Woop. oh| be | Sa ee es] cm ee 
BE eo) 2 | o@ | Se lee) sm ¥o 
2% Sb r ve Og |o™] He le 
3 o on 
fe ge; e | eo | ee 8'| as ea 
= Ho| 5 | @ [AGIA | AE i 
[ns In, jIn.| In, |In 
.817| 2000 Broke, 84) .20) £165) 125 
415) 1190! Broke.| 2.21 +43). 169} .088 
+422 36] 6176) O71 
the total number of fibres formed during the year, becoming greater the 
greater the number of thickened fibres. Thus it is seen that in Z, by far 
the strongest of the three pieces tested, the thick-walled fibres occupy 
almost half the year’s growth, while in # they form a mere strip at the 
end of the growth. In connection with this statement it may be well to 
remark that the absolute breadth of the annual growth in the coniferous 
woods does not seem to be as important an element in the problem of 
strength as in the so-called ‘ hard-woods ’’ (Angiosperms). The reason of 
this is the absence of the ducts which in the ‘hard woods”’ are formed, 
as a rule, in the early part of the annual growth. After this the solid 
wood is formed. Hence, the value in them, other things being equal, of 
a large annual growth. 
The ease with which the results of the tests upon the coniferous woods 
are explained gives place to the greatest difficulty in the case of the hard 
woods. Important factors in this case, and ones which we have not been 
called upon to consider in the coniferous woods, are, Ist, the weakness due 
to a greater or less abundance of ducts, and second, the strength added by 
more or less highly developed medullary rays.* The following table con- 
tains the results of eight experiments as to transverse strength made in 
exactly the same manner as described in the previous case. The pieces of 
timber were in all cases carefully selected and accurately dressed. They 
*The medullary rays being much less conspicuous in the Coniferse, 
ti 
