VOL. I.XIII.] PHILOSOPHICAL THANSACXIONS. 373 



each magazine, a well should be dug in or through the chalk, so deep as to have 

 in it at least 4 feet of standing water. From the bottom of this water should 

 arise a piece of leaden pipe, to or near the surface of the ground, where it should 

 be strongly joined to the end of an upright iron bar, an inch and half diameter, 

 fastened to the wall by leaden straps, and extending 10 feet above the ridge of the 

 building, tapering from the ridge upwards to a sharp point, the upper 12 inches 

 of copjier, the iron to be painted. We mention lead for the underground part 

 of the conductor, as less liable to rust in water and moist places; in the form of 

 a pipe, as giving greater stiffness for the substance; and iron for the part above- 

 ground, as stronger, and less likely to be cut away. The pieces, of which the 

 bar may be composed, should be screwed strongly into each other, by a close 

 joint, with a thin plate of lead between the shoulders, to make the joining or 

 continuation of the metal more perfect. Each rod, in passing above the ridge, 

 should be strongly and closely connected by iron or lead, or both, with the 

 leaden coping of the roof, by which a communication of metal will be made 

 between the 1 bars of each building, for a more free, and easy conducting of the 

 lightning into the earth. 



We also advise, in consideration of the great length of the buildings, that 1 

 wells, of the same depth with the others, should be dug within 1 2 feet of the 

 doors of the 2 outside magazines; that is to say, one of them on the north side - 

 of the nortli building, the other on the south side of the south building; from the 

 bottom of which wells, similar conductors should be carried up to the eaves, 

 there joining well with a plate of lead, extending on the roof up to the leaden 

 coping of the ridge, the said plate of lead being of eijual substance with that of 

 the coping. We are further of opinion, that it will be right to form a com- 

 munication of lead from the top of the chimney of the proof-house to the lead 

 on its ridge, and thence to the lead on the ridge of the corridor, and thence to 

 the iron conductor of the adjacent end of the magazine; and also to fix a con- 

 ductor from the bottom of the weathercock spindle of the clock-house, down on 

 the outside of that building, into the moist earth. 



As to the board-house, we think it already well furnished with conductors, by 

 the several leaden communications abovementioned, from the point of the roof 

 down into the water, and that, by its height and proximity, it may be some 

 security to the building below it; we therefore propose no other conductor for 

 that building, and only advise erecting a pointed iron rod on the summit, similar 

 to those before described, and communicating with those conductors. 



To these directions we would add a caution, that in all future alterations or 

 repairs of the buildings, special care be taken that the metalline communications 

 be not cut off or removed. It remains that we express our acknowledgments 

 to Sir Charles Frederick, Surveyor-general of the Ordnance, for the obliging 



