J48 I'HILOSOPHICAL TRANSACTIONS. ." [ANNOI764. 



elastic fluid, previously disturbed by various causes. Now, according to the laws 

 of elastic fluids, the endeavour to restore the equilibrium of such a fluid, will be 

 in that direction where the resistance to its passage happens to be the least. On 

 this principle we therefore see a necessity, either to open a passage for it to go 

 freely through, by placing certain bars of metal properly, or, to stop the passage 

 of the fluid through such buildings entirely. The last method would be dan- 

 gerous to put in practice; because, if high buildings were so secured, the light- 

 ning would then attack, the lower buildings, which are far more numerous, and 

 probably would destroy a greater number of people, cattle, &c. Whereas, if 

 the first method is preferred, the high buildings will then tend to protect the 

 lower ones more effectually ; and may with propriety be considered as so many 

 pipes to carry off^ the lightning quietly, either from the earth to the clouds, or 

 from the clouds to the earth. And that several proper conductors are necessary 

 to carry off" the lightning more readily, than some of the accidental or partial 

 conductors in a large town are capable of, appears from this; that we are able 

 to collect small quantities of the electric fluid, with a slender apparatus in our 

 hands only; whilst it is exposed in the street, garden, or other open place, dur- 

 ing the hovering of such clouds as occasion violent lightning. 



From repeated observations of this kind, there is reason to believe that the 

 quantity of lightning at particular times, is so very great, that it would be dan- 

 gerous to invite it to any buildings, and that unnecessarily, in the most powerful 

 manner we are able; by suffering the several conductors to end in a point at the 

 top. On which account, it is apprehended that pointed bars, or rods of metal, 

 ought always to be avoided. And as the lightning must visit us some way or 

 other, from necessity, to restore the equilibrium, there can be no reason to invite 

 it at all ; but, on the contrary, when it happens to attack, our buildings, we 

 ought only so to contrive our apparatus, as to be able to carry the lightning away 

 again by such suitable conductors, properly fixed, as will very little, if at all, 

 promote any increase of its quantity. 



To attain which desirable end, in some degree at least, it is proposed that the 

 several buildings remain as they are at the top; that is, without having any metal 

 above them, either pointed or not, by way of a conductor. On the inside of the 

 highest part of such building, and within a foot or two of the top, it may be 

 proper to fix a rounded bar of metal, and to continue it down along the side of 

 the wall to any kind of moisture in the ground. But if the building happens to 

 be mounted with an iron spindle, for supporting a vane, or other ornament, and 

 it should not be convenient to have it taken away, then the bar of metal ought 

 to communicate with that spindle. And as to the diameter of such a metal bar, 

 it will probably depend on the height of the building; for it is apprehended the 

 great church of St. Paul's, to complete the partial conductors (which are the me- 



