PRESERVATION OF METALS USED IN MARINE CONSTRUCTION. 165 



effect of the zinc. These samples, which I will exhibit, have been submerged only 

 about seventy-two hours and show in a striking contrast the corrosion of one, and 

 its absence on the other. That is the sample with the zinc on it (indicating sample) , 

 and that is the zinc protector. There is practically no corrosion at all on the steel. 

 This sample, which has copper only, as you see, is badly corroded. 



The statements as to lack of advantage of using galvanized steel plating is 

 hardly borne out by the experience in connection with older torpedo craft, some of 

 which had their under-water bodies built of black plating. These have corroded 

 much more rapidly than others where galvanized plating was used. 



Another point to which I call attention in connection with the statements in 

 the paper as to the corrosion of salt-water piping, is the fact that this difficulty has 

 been solved effectually on U. S. naval vessels by the use of lead-lined pipe for such 

 purposes. This has eliminated the difficulties referred to. 



Chief Constructor R. M. Watt, Vice-President: — As I was absent from the 

 room when this paper was discussed, I desire to communicate the experience of the 

 Navy Department in connection with the inference that might be drawn from the 

 statements appearing at the bottom of page 151. 



Lines of suction and discharge piping are continued through the inner bottoms 

 of naval vessels by sea chests. Sea chests were first made of cast steel, and out- 

 board deUvery piping was made of wrought steel tubing, whereas the lines of piping 

 were in many instances ofcopper. When sea chests were made of cast steel, a not 

 infrequent item of repairs to naval vessels was the renewal of steel sea chests because 

 of the corrosion and pitting at the inboard end where it was impracticable to fit zinc 

 protectors. Accordingly, a large-scale test was determined upon, and the U. S. S. 

 Massachusetts was selected for the purpose, inasmuch as her starboard outboard 

 delivery tube had been renewed three times, and the port outboard delivery tube 

 had been renewed twice in a period of commission of less than five years. The 

 experimental substitution of composition tubes for the wrought steel tubing was 

 ordered. Around a rectangular opening through the shell plating a reinforcing 

 plate was fitted, to which the composition casting attached, and a zinc protector 

 was fitted flush with the outside plating in the opening through the shell plate. 

 When examined a year later the tubes were found to be in the same condition as 

 when installed, the zinc showing unmistakable evidence of attack and requiring 

 renewal. There was no pitting of the reinforcing plate and none of the outside plat- 

 ing, except some very sUght pitting for three or four inches abaft the zinc. This 

 pitting has been eliminated in later vessels by extending the zinc protector further 

 abaft the opening. The results obtained were so satisfactory that all sea chests 

 and outboard deliveries were afterwards, and are now, made of composition, and 

 their renewal in recent years has been most infrequent. 



Lieutenant-Commander Lyon (Communicated): — Having read very care- 

 fully the discussion of his paper by Naval Constructor Williams the author can 

 only state as follows: He had no intention of placing himself in the attitude of 



