160 Mr Harris o« the Utility qffiaing 



electric matter being then enabled to produce all the disastrous 

 effects of an expansive force, as if, whilst in the conducting 

 body, it was in a diffused and low state, and again condensed 

 and brought into a narrow focus, at the moment of leaving it. 

 The damage, therefore, may be in this case considered to hap- 

 pen, not where the best conductors are, but where they are not ; 

 so that the mariner has to contend with a constantly exploding 

 principle, which continues its devastations in all those points 

 where it ceases to be transmitted ; thus determining for itself a 

 passage between the points of action through such line or lines 

 as may, upon the whole, oppose to it the least resistance. 



11. Such effects being constantly observed not only on ship- 

 board, but on shore, it became a grand question of scientific 

 consideration, how far it would be prudent to provide for the 

 electric matter an efficient conducting line, between the highest 

 points of a ship and the sea, so as to offer the least resistance to 

 the progress of such a powerful agency, and transmit it in a 

 state of low tension between the points of action ; on the same 

 principle that persons, dreading an inundation, would provide a 

 channel to carry off the water as easily as possible ; an idea, as 

 is well known, first suggested by the celebrated Dr Franklin, 

 and since carried into practice with considerable success ; the 

 conducting line having the name of Lightning-Conductor or 

 Lightning- Rod. 



12. Although the application of lightning-conductors to 

 buildings on shore is always judicious, and their advantages 

 very apparent, yet on ship-board, where the effects of lightning 

 are most to be dreaded, the introduction of this means of de- 

 fence has been slow and imperfect. The conductor hitherto 

 employed at sea consists of long flexible chains or links of me- 

 tal, about the size of a goose-quill, sometimes of iron : those em- 

 ployed in H. M. Navy, however, are of copper ; they are usual- 

 ly packed in a box, and are intended to be set up from the 

 mast-head to the sea when occasions require, so that, as observed 

 by Mr Singer, in his excellent work on electricity, partly from 

 inattention, and partly from prejudice, they frequently remain 

 in the ship's hold during long and hazardous voyages quite un- 

 employed ; a remark, the truth of which is but too frequently 



