488 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



for the protection of boilers from incrustation, remarks that 

 such a combination has been found very injurious, on ac- 

 count of the galvanic action of the two metals, and that 

 more satisfactory experiments are required, with waters of 

 different qualities, particularly with the acid water common 

 in coal-mines, before much reliance can be placed upon the 

 so-called improvement. Engineering and Mining Journal, 

 June 26, 478. 



ELECTRIC FUSES. 



A series of memoirs and discussions on the subject of elec- 

 tric fuses and the efficiency of torpedoes, submarine blasting 

 operations, etc., has occupied the attention of the Society of 

 Telegraphic Engineers; and among the papers presented, 

 especial interest attaches to that of Professor Abel, on ac- 

 count of his extensive experience in these matters. He 

 holds the opinion that the many disappointments and acci- 

 dents that have occurred in connection with electric fuses 

 are, in general, not to be attributed to the electricity nor 

 to the fuses, but rather to the carelessness of the operators. 

 It can always be shown by a preliminary calculation wheth- 

 er a given galvanic battery can possibly heat a fine wire 

 white hot, or whether it will fail to heat it hot enough to 

 explode the fuse. His own experiments confirm the prac- 

 tice of some American constructors of torpedoes, in finding 

 that both German-silver and platinum-silver alloys are great- 

 ly superior to platinum in regard to the resistance opposed 

 to the passage of the electric currents, and consequently de- 

 velop greater amounts of heat for wires of given lengths and 

 diameters. German silver is superior in this respect to 

 platinum silver. The most insidious cause of failure of elec- 

 tric fuses is found in the corrosion due to moisture ; and for 

 the construction of low tension fuses the wire must be se- 

 lected wiiich possesses the power of resisting corrosion when 

 in immediate contact with the material of which the fuse is 

 formed. In this respect German -silver wires, although in- 

 closed in tubes, were found to deteriorate very slightly dur- 

 ing the first forty days of their exposure, while platinum-sil- 

 ver wires in close tubes remained constant. When the gun- 

 powder is wet, the German silver has much greater liability 

 to corrosion. The charcoal is apparently that element of 



