Ltightning Conductors in Ships. 355 



long elastic continuous line ; the whole conductor is inserted under 

 the ed§es of a neat groove, ploughed longitudinally in the aft side of 

 the different masts, and secured in its position by wrought copper 

 nails, so as to present a fair surface. The metallic line thus con- 

 structed, will then pass downward from the copper spindle at the 

 mast-head, along the aft sides of the royal-mast and top-gallant-mast, 

 being connected in its course with the copper about the sheeve-holes. 

 A copper lining in the aft side of the cap, through which the top- 

 mast slides, now takes up the connection, and continues it over the 

 cap, to the aft side of the top-mast, and so on as before, to the step 

 of the mast. Here it meets a thick wide copper lining, turned round 

 the step, under the heel of the mast, and resting on a similar layer of 

 copper, fixed to the keelson. This last is connected with some of 

 the keelson-bolts, and with three perpendicular bolts of copper, of 

 two inches diameter, which are driven into the main keel upon three 

 transverse or horizontal bolts, brought into immediate contact with 

 the copper expanded over the bottom. The laminae of copper are 

 turned over the respective mast-heads, and secured about an inch or 

 more down on the opposite side ; the cap which corresponds is pre- 

 pared in a somewhat similar way, the copper being continued from 

 the lining in the aft part of the round hole, over the cap, into the 

 fore part of the square one, where it is turned down and secured as 

 before, so that when the cap is in its place, the contact is complete. 

 In this way, we have, under all circumstances, a continuous metallic 

 line, from the highest points to the sea, which will transmit the elec- 

 tric matter directly through the keel,* being the line of least re- 

 sistance. 



16. From what has been already observed, it will be apparent, 

 that, in whatever position we suppose the sliding-masts to be placed, 

 whether in a state of elongation or contraction, still the line of con- 

 duction will remain perfect, for that part of the conductor which ne- 

 cessarily remains below the cap and top, when the sliding masts are 

 struck, is no longer in the line of action, consequently its influence 

 need not be considered. 



17. The following table exhibits the mean proportion of a con- 

 ductor thus constructed on one mast of a fifty gun frigate, as com- 



* Since the mizen-mast does not step on the keelson, it will be necessary to have 

 a metallic communication at the step of the mast with the perpendicular stancheon 

 immediately under it, and so on to the keelson as before, or otherwise carry the con- 

 ductor out at the sides of the- vessel. 



