PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 487 



should be made known. The Manhattan Firearms Co., of Newark, N. J., 

 the manufacturers, spared no pains or expense to make a perfect tool, and 

 I would advise every one interested in metal working to send for samples. 



The best fine tools we have in this country are not made here but abroad. 

 I mean by this, small riinnu'rs, screw plates and similar wares; and I think 

 that, as members of this association, we should take pains to make the 

 facts I have previously stated widely known. 



Mr. Arnold, the inventor of machinery for making- the drill, was piesent 

 and gave some interesting information as to the manufacture of the tool. 



S. H. Maynard. — I should like to have the inventor state how he tempers 

 the drills. Does he mean to say that he does not lose any of them, and 

 that they do not buckle or twist in hardening ? 



Mr. Arnold. — I can answer that question by sajnng that we harden them 

 by plunging the shank end in the water first and draw the temper after- 

 wards to the right color. The taper on the length of the drill, 12 inches, 

 is barely the sixty-fourth of an inch and we rarely find any so bent that 

 they are useless; a little deviation can easily be corrected by a hammer. 

 Mr. Arnold stated that the drill was never touched by a hammer to be 

 forged from the time the steel was drawn, and was therefore homogeneous 

 throughout., ^ 



Telegraphs. 



The subject for the evening, " Telegraphs," was taken up, when Mr. T. 

 D. Stetson gave a detailed account of the various submerged cables that 

 have been laid, and the methods adopted to overcome the difficulties 

 experienced in their working. A large part of those submerged on the 

 Eastern continent have ceased to work well, without any well defined 

 cause being given. The practical working of a cable coiled in a tank filled 

 with water, such as the new Atlantic cable is being subjected to, does not 

 argue the same result as when placed at the bottom of the ocean, as there 

 difi'erent influences are at work. He had considerable doubt in his mind, 

 notwithstanding all that had been said on the subject by what may be called 

 good authority, whether there has ever been a dispatch sent through the 

 first Atlantic cable after it was laid; although we have credible accounts 

 of dispatches being sent through one line in the Mediterranean 1,700 miles 

 long, most of which was submerged. Mr. Stetson here exhibited a speci- 

 men of the new Atlantic cable, now being finished in England, which is 

 made on nearly the same principle as the first one, only being about twice 

 the size of the old one. 



Dr. R. P. Stevens said there appeared to be some radical defects in the 

 plan of telegraphing across the Atlantic ocean. If unfortunately the cable 

 should break, it would be a very difficult matter to mend it, and a continu- 

 ous wire of some 2,300 miles at the bottom of the ocean, where no defect 

 can be seen, is hardly to be expected. The next question is, how long will 

 the material last of which the cable is composed. I feel convinced that it 

 will decay at the bottom of the ocean. At the present time the ocean con- 

 tains salts of copper and acids that will affect the metal covering of the 

 wire, and the vegetable matter, such as the hemp and gutta percha used in 

 its construction must sooner or latter be destroyed. There are scavengers 



