290 On Lightning Conductors to Powder Magazines. [No. 99. 



vate observations of Mr. (James) Prinsep, which do not appear, 

 the Governor General's opinion seems to have been formed. 



7. First, I infer from the general tendency of the observations 

 of these gentlemen, that they entertain the notion that lightning 

 conductors have the power of attracting a discharge of lightning 

 to places where without them it would not occur. 



8. Nothing can be more unfounded than this supposition. 

 The intense action which takes place between an electric cloud, 

 of the extent perhaps of many thousands of acres, and an equal 

 area of the earth's surface, is much too extensive to be materially 

 diverted by the mere point which can be directed upon the lat- 

 ter; and which, as compared with the extent and distance of 

 the charged clouds, must be quite inconsiderable. The path of 

 the discharge which takes place, in the form of lightning is deter- 

 mined by what may be the line of least resistance in the whole 

 distance between the two great electrical surfaces, of which the 



, conductor can form but a minute, fractional part. 



/\ 9. Over this fractional part, however, we may have control 

 sufficient for the protection required. It has been well and ac- 

 curately observed, "that lightning conductors can no more be 

 said to attract the matter of lightning, than a water course can 

 be said to attract the water which necessarily flows through it at 

 the time of heavy rain. 5 ' It would be absurd to say that a hollow 

 water-pipe open at its upper end, and placed perpendicularly, at- 

 tracts or invites rain from the clouds, or that in providing our 

 houses with such pipes, we incur a greater risk of being inundated, 

 because they are calculated to discharge freely all the rain which 

 passes into them. No less absurd is it to say that a metallic rod 

 invites lightning, and may be productive of damage, because it is 

 calculated to transmit the electricity which falls on its point.* rV) 



10. Secondly, Dr. O'Shaughnessy refers to danger which is 

 likely to occur from the erection of conductors in the contiguity 

 of powder magazines from what is called " lateral discharge." 



* A pointed conductor will indeed draw off silently and safely a consi- 

 derable portion of electricity from a charged cloud, but it .can possess no 

 power of determining a disruptive and destructive discharge at a point where 

 it would not otherwise occur. — Mr. Darnell's note. 



