396 
SEVENTH REPORT—1837. 
Comparative Results of Muirkirk Iron No.1. 
Distance between supports 4 ft. 6 in. and 2 ft. 3 in. 
a i 
Strength ofthe Cold Blast Iron,| Strength of the Hot Blast Iron,| Ratio of the Strengths. 
458-8 ) Mean 
423°8 ) Mean 
428-2 [ 443°5 412-0 f 417°9 1000 : 942 
979°3 ; 765-2 ; ai 
380.8 $9299 Gta } 839°8 1000: 912 
Mean ratio of strength...... 1000 : 927 
The products and ratio to resist impact. 
Product of streugth by ulti- 
mate deflection in Cold Blast 
Product of strength by ulti- 
mate deflection in Hot Blast 
Ratio of products, or of 
power to resist impact. 
Iron, Tron, 
ep \ 770-1 a } 656-8 1000: 852 
4365 ; 289°5 ‘ \ 
3780 ; 4072 357.8 $828 1000: 794 
Mean ratio of power to sustain impact...... 1000 : 823 
EEE eee eee ee 
Modulus of elasticity in ths. for a hase of an inch square. 
Cold Blast Iron...... 14,050,600 
IDIGUOs teres saecettesa=s 13,956,500 
Mean...... 14,003,550 
Hot Blast Iron...... 12,805,700 
[DattOwecddetsaseacesses 13,783,100 
Mean...... 13,294,400 
Effects of Time. 
In former experiments on the transverse strength of cast tron, 
it has been assumed that the elasticity remained perfect to the 
extent of rd at least of the breaking weight. This assumption, 
which has been attempted to be proved by Tredgold, has gained 
considerable credence ; but so far as I can perceive there ap- 
pears to be no ground for such an opinion. In the earlier ex- 
periments on the subject of hot and cold blast irons, it was ob- 
served by Mr. Hodgkinson that in some cases the elasticity was 
considerably injured with 4th or jth of the breaking weight. 
This fact was of such importance as to induce me to pay consi- 
derable attention to the set in the preceding tables,and also to 
note the defects of elasticity in those that follow, up to the time 
