234 On the Transverse Strain, 
son* has shown in his valuable Essay on the 
Strength of Materials, in the Encyclopedia 
Britannica) it is, when applied to timber, 
highly erroneous. 
11. Dr R. quotes some experiments of Du 
Hamel, which, as they appear to be very 
interesting, I will transcribe. ‘They are as 
follow: “ He took 16 bars of willow, 2 feet 
long, and = an inch square, and supporting 
them by props under the ends, he broke them 
by weights hung at the middle. He broke 
four of them by weights of 40, 41, 47, and 
52 pounds; the mean is 45. He then cut 
four of them 3 through on the upper side, 
and filled up the cut with a thin piece of 
harder wood stuck in pretty tight. ‘These 
were broken by 48, 54, 50, and 52 pounds ; 
the mean of which is 51. He cut other four 2 
through, and they were broken by 47, 49, 
50, and 46 pounds; the mean of which is 48. 
The remaining four were cut 3ds; and their 
mean strength was 42.” 
‘«« Another set of hisexperiments,” continues 
the Doctor, “‘ were still more remarkable. 
Six battens of willow 36 inches long and 12 
* And more recently Mr, Peter Barlow, in his excellent 
« Essay on the Strength and Stress of Timber”— a work 
which I was unacquainted with when this paper was read. 
