4 THE LATE MR. WILLIAM STURGEON ON 



the fluid from the non-conducting air into the land, through 

 the medium of its vegetable clothing, would necessarily move 

 it still farther in this better conductor, which would neces- 

 sarily become electro-negative throughout a much greater area 

 than that presented by the lower surface of the cloud. Hence 

 there appears but little difficulty in understanding why trees, 

 which present multitudes of conducting points and sharp edges 

 to the air, and stand more prominent than the ordinary level of 

 the vegetation, should so frequently be the victims of lightning. 

 It is, however, worthy of remark, that the tallest trees are 

 but seldom selected ; and frequently lightning strikes objects 

 closely situated to trees without touching the latter. The 

 nature of the soil, with regard to its conduction, as well as 

 the objects situated on it, has much to do with the reception 

 of lightning, for no object can receive a discharge from a 

 cloud unless it be susceptible of electro-negation by the 

 cloud's repellent force; hence objects situated on wet lands 

 or on the banks of rivers are frequently those which fall 

 victims to lightning. Heavy rains, however, render all 

 objects, as well as the sites on which they stand, conductors, 

 and consequently susceptible of electro-polarisation by the 

 repellent force of a thunder-cloud. 



59. Wherever land is impervious to the electric fluid, that 

 in the air above it becomes accumulated in a stratum on its 

 surface on the approach of a disturbing thunder-cloud, and 

 the repellent forces of the positive stratum, and those of 

 the cloud, cause the latter to diverge from the direction of 

 the wind, until it arrives at a locality suitable for the intro- 

 gression of the disturbed electric fluid of the air. Hence it 

 is obvious that the removal of the electrical resistance of the 

 air is a necessary preliminary to lightning striking objects on 

 the earth's surface, for the force that repels the cloud is that 

 which counterchecks the tendency of lightning discharges. 



60. But if a displacement of the electric fluid of the air 

 be a necessary preliminary to strokes of lightning, and it 



