961 



Having ascertained the comparative value of the dijfterent manu- 

 factures of plate-iron, the author, by another class of experiments, 

 investigated the different methods in use of joining the plates together 

 by rivets. This appears to be an important section of the inquiry, as 

 the relative strength of each description of joint within reach of the 

 experiments is clearly ascertained, and their/elative values of strength 

 determined in reference to each other, and to the plates themselves. 

 These were found after a careful investigation to be nearly as the 

 numbers 100, 70 and 56 ; that is to say, the plate being taken at 100, 

 the double-riveted joint was 70, and the single-riveted joint 56. 



The resisting powers of plates, and the different kind of joints by 

 which they are united, having been proved, the paper goes on to in- 

 vestigate the value of the different kinds of timber when applied to 

 a similar purpose, and by a careful comparison of the results, it is 

 ascertained that the tensile powers of each, compared with iron, 

 amber representing unity, are in the following ratio, viz. 



Ash as 1 : 2*94^ 



Teak as 1 : S'SS 



Fir (good) as 1 : 4-16 

 Beech as . - . 1 : ^'S^ 

 Oak as 1 : 5-00 



From the above it is inferred by the author, that iron being five 

 times stronger than oak, a vessel built of that material is neither so 

 strong, nor yet so secure, as the iron ship. 



The next subject of inquiry is the transverse strength of angle- 

 iron, T'^^'O^^ other sectional forms which enter into the con- 

 struction of the beams, frames and ribs of ships. These combina- 

 tions were likewise put to the test of experiment. In this part of the 

 inquiry it was soon ascertained that bars of angle-iron used for that 

 purpose are not of the best form, but exhibited great weakness when 

 compared with wrought-iron beams of the S form, having flanges on 

 both sides. From these results the author recommends that a com- 

 bination of angle-iron should be used for these objects, as explained 

 in the paper, and shown in the diagrams which accompany it. 



In order to render the inquiry of practical value, experiments 

 were made on the resisting powers of plates, by forcing a blunt in- 

 strument with hemispherical end of three inches diameter through 

 the plates. These experiments were again repeated under similar 

 circumstances upon timber, and a comparison is drawn from these 

 data as to the resisting power of each. These experiments are in- 

 teresting so far as they establish the superior strength of iron when 

 exposed to severe strain, as frequently occurs in vessels taking the 

 ground upon boulder-stones, or any uneven surface. 



These results being obtained, the author closes the paper with a 

 series of experiments made at Woolwich Dockyard on the strengths 

 and elongation of iron-bars. In this department some curious results 

 are obtained, such as the fact that an iron bar, when elongated to a 

 considerable diminution of its sectional area, was not reduced but 

 rather increased in strength ; and after repeated experiments, it was 

 found that wrought-iron bars, when elongated or wire-drawn, were 



2 



