\/A- WILLIAM SIEMENS, r.R.S. 463 



tion. X' verthcless, in order to induce us to fall in with the new 

 Rule, the pressure was reduced after each voyage :> Ihs., and we 

 should verv so. m liiive been in tho happy condition of depending 

 upon our sails. The operations that have to be carried on on 

 l>o;u.l this ship arc so important, that I decided to have steel 

 boilers put in, at an expense of 10,000, although the inspection 

 of the boilers proved that they were in perfect condition. Now, 

 this is a hard case to me as a shipowner, because if the two 

 authorities had been agreed regarding the Rules, I should not 

 have been put to this expense, and have had to sell good boilers 

 second-hand, which have gone into other ships not requiring to be 

 under the rules of the Board of Trade. As an engineer, and one 

 interested in the manufacture of materials, I should say that the 

 Board of Trade Rules give us excessive thicknesses, especially in 

 cases where first-class material is used. I see on page 79 that 

 certain strengths of iron are assumed, not according to the tests 

 this iron can stand, but it is taken to be equal to 47,000 Ibs. per 

 square inch in the one direction and 40,000 Ibs. in the other. 

 Now this seems to involve a condition of things which does not 

 exist that of all materials being equally good. I would rather 

 say, have each plate, whether it be steel or iron, tested, and if it 

 does not stand an elongation of 20 per cent, in a bar 8 inches 

 long, it ought to be considered unfit for being put into a boiler. 

 Mr. MacFarlane Gray has given us his reasons why the Board of 

 Trade insist upon a thickness of plate exceeding, as he admits, the 

 necessities of the case. He has given us an instance where, at a 

 pressure of only 17 Ibs., a plate had cracked all along the seam, 

 although the boiler was expected to stand 70 Ibs. But I fail to 

 follow Mr. MacFarlane Gray in his argument. The forces that 

 come to bear (viz., the strains) upon the material through expan- 

 sion by heat increase enormously with the resisting power of that 

 material, and therefore the very fact which Mr. MacFarlane Gray 

 has brought before us, appears to me to tend rather in the direc- 

 tion of avoiding excess of thickness, because with excess of thick- 

 ness you get always, whatever be the nature of the material you 

 employ, an inferior plate. But, I say, have sufficient thickness, 

 and be more careful regarding the quality of the material which is 

 employed. If the material of which that boiler was constructed 

 had been such as would elongate 20 or 30 per cent, before break- 



