446 THE SCIENTIFIC PAPERS OF 



they were taken back to the works to be annealed. I am disposed 

 to take considerable objection to that procedure. Mild boiler 

 steel should bear any amount of rough work in a cold condition 

 without receiving the least injury. If by punching mild steel 

 you lose strength, I consider you have a clear proof that the 

 material is not what it should be. So far from diminishing its 

 strength, the very act of punching should increase the strength of 

 the material. In fact, any treatment to which mild steel is sub- 

 jected, straightening or punching it, or straining it in any one 

 place, so as to alter slightly its form, the effect invariably is 

 increase of strength, and not a slight increase of strength either. 

 It is, therefore, a practice with which I have little sympathy, that 

 of annealing plates after punching. I would prefer to see the 

 metal used, after it has been punched, without being annealed, 

 and if it is a proper metal it should not require annealing, except 

 in case it had been partially heated in a smith's fire. If the holes 

 are afterwards bored to make the edges smooth, that may be 

 desirable to give more elegant work, but for the mere sake of 

 getting strong and reliable work, I do not believe that it is necessary. 

 Punching alone should give you the full strength of the metal 

 when the work is put together. Therefore, what we should know, 

 in order to judge this question more fully, is the exact mode in 

 which the metal was treated after it had been made, what sized 

 ingots were cast, and were those ingots hammered before they 

 were rolled ; if they were reheated, as they were undoubtedly, 

 what kind of furnace was used, and were they allowed to remain, 

 as sometimes happens, a night in the furnace. Then, again, Mr. 

 Thornycroft has already alluded to the processes of annealing 

 which are sometimes adopted : I think there is great danger in 

 annealing steel plates ; only if a steel plate has been heated in the 

 forge fire, if it has been heated partially in order to bend it, 

 annealing is necessary, to put it as a whole in a natural condition ; 

 but if the metal has been worked cold, I believe it would be much 

 better to leave it unannealed. Then, again, annealing is not 

 always done in a proper and judicious manner ; if one plate only 

 could be put into a well-heated furnace, to take up rapidly the 

 temperature necessary in order to put the particles to rest towards 

 one another, and then could be taken out and allowed slowly to 

 cool, probably no danger would arise. But plates are heaped up 



