.S7A' WILLIAM SIE.Mi:.\ -S /.A'..s. 395 



the longitudinal tie-bolts, and these bolts were purposely made 

 long. If they were not naturally long he should make them long, 

 and lie should make them of steel containing at least <r5 per cent. 

 uf carbon ; because a bolt of that description would not only bear 

 ;i tensile strain of 50 tons per square inch with perfect safety, but 

 its length would allow fur all those variations in distance between 

 the Manges which from time to time had to be contended with. 

 .Men -over it must be borne in mind that each bolt partook of the 

 temperature of the boiler ; where the boiler was hotter the bolt 

 would be slightly hotter, and it would therefore adjust itself 

 naturally to its work in that respect. Accordingly he did not see 

 why a vessel constructed on this plan should become leaky through 

 heating unequally in the way in which a marine boiler was heated 

 unequally, that is, less at the bottom than at the top. 



It had also been suggested by Mr. Adamson that it might be 

 better to weld the circular flanges together. The objections he 

 would urge against that plan were that the welding would intro- 

 duce, to begin with, a great deal of labour, the material might be 

 found to be injured, and the tensile strength of the material would 

 certainly be very considerably reduced in the longitudinal direc- 

 tion. In the preceding paper there had been under consideration 

 boilers constructed of very mild steel But in this construction he 

 proposed a departure from that principle as regarded the outer 

 shell of the boiler. Instead of steel capable of bearing 28 or 

 30 tons tension per square inch, he would employ a material that 

 would stand 45 tons per square inch. If such a material were 

 to be riveted, it would be unreliable ; or if there were to be holes 

 bored in it, however carefully, for the reception of bolts, it would 

 Rtill be unreliable. But if a ring of such metal were rolled, the 

 rolling being in the direction in which its strength was required, 

 it might, provided its continuity was not broken in any way, be 

 loaded up to one-half of its breaking strength with the utmost 

 safety. The result was that he could get on these rings a working 

 load of 1 5 tons per square inch, or probably more than double the 

 amount he otherwise would venture to put upon the metal. There- 

 fore he maintained that this was a light construction. 



Attention had been drawn by Mr. Hawksley in the preceding 

 discussion to the fact that very pure metals were more apt to 

 corrode than metals containing a higher proportion of carbon, such 



