78 On the Sea-cell as a Possible Source 



4. Exploded through about 14 yards. 



5. Exploded through about 24 yards. 



6. Exploded through about 41 yards at moment of con- 

 tact, showing that the fuse was of great comparative sensi- 



, tiveness. 



7. Exploded through about 21 yards. 



8. Exploded through about 17 yards, but only after long 

 contact. 



By actual measurement the resistance of the wire used 

 gave 1 Ohm to 175 yards. The proportion of 175 to 126"8 

 is very nearly as 7 to 5. If, therefore, we take five-sevenths 

 of the length of wire used by Messrs. Caldwell and Smibert, 

 we get very nearly the corresponding lengths of wire of the 

 same resistance as that used in the Queenscliff experiment. 



The fuses used were sent out to the colony some years ago 

 for use in the Torpedo Corps, and, it is to be presumed, were 

 manufactured with proper care in the Government work- 

 shops at home. By measurement, I find the resistance of 

 them to vary from about '6 to about *7 Ohm ; but I cannot 

 say what current is supposed to be sufficient to fire them, as 

 I do not know the size, &c, of the wire employed. I can 

 only say that they were regulation fuses, for use in torpedo 

 work, and that they were not " made for the occasion." 



From these experiments, in connection with some tests 

 with the galvanometer, Mr. Caldwell suspected that in the 

 hull of the " Cerberus" there was a more potent metal 

 exposed than iron, and he concluded that, possibly, there 

 were some copper surfaces connected with the vessel exposed 

 to the action of salt water. He ascertained that a sheet of 

 zinc, 7 feet by 3 feet, in conjunction with a sheet of copper 

 18 inches square, will unfailingly fire these regulation fuses 

 through short lengths, say about 12 feet of the wire usually 

 employed. 



My calculations have reference to the power of an iron 

 and zinc sea-cell ; but the presence of an exposed surface of 

 copper in the bottom of the iron vessel would, undoubtedly, 

 increase the electromotive force of the ceil. Now, it is a 

 fact that in the bottom of the " Cerberus" there is an 

 amount of copper surface exposed to the action of the sea- 

 water, and the same may be said of R.M.S. " Malwa." 



With reference to the experiments from the "Malwa," 

 however, the consideration must not be lost sight of that in 

 the sea-water just within the entrance at the Heads there 

 is a much larger proportion of salt than there is in the 



