72 On the Sea-cell as a Possible Source 



the accident that the explosion did not occur through an 

 accidental contact through or by means of the firing key. 



A casual conversation with the President of this Society 

 induced me to give some attention to the sea-cell current as 

 a possible cause of the accident, and at his request I embodied 

 the results in a memorandum which the Board published as 

 an appendix to its report. 



Now, if the reasoning in that memorandum were unsound, 

 it could have been shown to be so ; my calculations were 

 equally open to correction. But those who have objected to 

 my conclusions have not attempted to show that there is 

 any fallacy in the one or the other. They have contented 

 themselves with denying the conclusions ; and some who 

 have spoken as with authority have boldly, and, as I think, 

 rashly, asserted that it is impossible for the explosion to 

 have been caused by a sea-cell current. 



The question, however, can hardly be considered as finally 

 disposed of by such objectors. Mere assertion is not argu- 

 ment; and as the question is by no means exhausted, I have 

 thought it desirable to bring together in this paper such 

 considerations as seem to be salient to the subject, to view 

 them in the light of some recent experiments, and to invite 

 the members of this Society to give the subject a more 

 thorough and scrutinising examination than it has hitherto 

 met with. 



In doing so I shall, of course, have to repeat the substance 

 of the memorandum I have referred to. I have since been 

 informed, however, that the wire used in the fatal experiment 

 was No. 16 B.W.G., and not No. 15 B.W.G., as I had been 

 given to understand. This has rendered necessary some slight 

 alterations in my calculations as to lengths of wire through 

 which fuses may be expected to explode, and I only mention 

 the fact for the benefit of those who may be at the trouble 

 of comparing the two documents. 



It appears that the case containing the fatal charge was 

 of zinc. Now, it is a common practice to attach the earth- 

 wire of the charge to the metal case, which thus becomes 

 the earth plate. I do not know whether this course was 

 adopted in the QueensclifT experiment; but if it was not, it 

 is easy to understand how the earth connection, though left 

 loose, might come into contact with the zinc. And if we 

 further assume that some portion of the copper of the firing 

 linecameinto contact with the iron body of the " Cerberus," the 

 zinc, the iron, and the sea constituted what is termed a sea- 



