on the Strength of Materials. 169 
No. Ibs. oz. 
69 Hard gun-metal .. = -- 3 Oin the scale. 
70 Fine yellow brass .. ole aioe lt 
71 Copper, cast ee <= way UsPhike 
72 Tin we ae ie wa) ae 
73 Lead ae ‘ ts sist ae 
On Twists of different Lengths. 
Horizontal. Vertical. 
No. Weight in Scale. No. Weight in Scale. 
7A ibyslong 7 3 77 3 by Z do. 10 
75 1 by i do. B21 78 + by 2 do. 8 9 
76 ibylinchdo.8 8 | 79 iby linchdo. 8 5 
Horizontal twists at 6 from the bearing. 
80 2 by 6 inches long ae fe dO. 9 
81 i by do. do. ee oe ne ae 
82 1 by do. do. or ys 1. ADA of 
Twists of $ inch square bars, cast horizontally. 
No qrs. Ibs. oz. 
83 + close to the bearing 3 9 12 end of the bar hard. 
84 4 do. ae a 2 18 O middle of the bar. 
85 + at 10 inches from bearing, 124 0% 
lever in the middle 
On Twists of different Materials. 
These experiments were made close to the bearing, and the 
weights were accumulated in the scale until the substances were 
wrenched asunder. 
No. Weight in Scale. Weivht in Scale. 
86 Cast steel .. 19 9 {91 Hard gun-metal 5 0 
87 Shear steel .. 17 1 | 92 Fine yellow brass 4 ll 
88 Blister steel .. 16 11 }|93 Copper .. Bey aera 
89 English iron, No.1. 10 2 | 94 Tin i ae bid 
90 Swedish iron 9 8| 95 Lead ae ype bog 
Remarks. 
Here the strength of the vertical bars still predominates. 
The average of the two taken conjointly, and compared with 
* In the resistance to twisting there are some doubts by different writers 
expressed respecting the eflect of the length: these experiments, however, 
do not appear calculated to remove them, they are so extremely irregular. 
The angle of torsion was not observed, though it certainly would not have 
been difficult to have done so in the longer pieces. Some experiments on 
lurger specimens are described in Lhomson’s Annals for March 1819; but 
we cannot compare them with these, for want of a more currect knowledge 
of the nature of this strain. —T. T. 
+ These experiments are merely a repetition of those in a preceding page, 
experiments 64 to 73; except that here cast steel is stated tu be 19 Ibs. 9 oz. 
instead of 17 Ibs. 9 oz. 
a similar 
