PROTECTION AGAINST LIGHTNING. 811 



inquiry, and it was for this reason appropriately designated a " Perma- 

 nent Committee." The meteorologists concerned in its inauguration 

 were actuated by the same consideration that was present to the Sec- 

 tion of Physics of the Academy of Sciences in Paris when the follow- 

 ing paragraph of the instruction of 1854 was drawn up : 



One knows, it is true, a very great number of examples of people being killed 

 or of houses being set on fire ; one knows, also, many and diverse instances of 

 metals fused, of timber shattered, of stones and even of walls thrown far away, 

 and many other analogous effects ; but what is generally wanting is precise 

 measurements relative to distance, dimensions, the position of the object— both 

 that which is struck and that which escaped. For it is necessary to kmw what 

 the lightning spares, as well as what it strikes. It is the work of all observers, 

 but especially of officers in the navy and artillery, of engineers, of professors, 

 inventors, and architects, to test these phenomena at the moment they are pro- 

 duced, and to describe them accurately for the benefit of science, as well as that 

 of public economy. Such descriptions, when they refer to a stroke of lightning, 

 should as much as possible point out the track of the lightning from its highest 

 to its lowest point; also they should show, by sufficiently numerous horizontal 

 sections, the relative positions of all objects in a circle wide enough to take in 

 those which have been struck. 



In this passage the instruction of the French Academy no doubt 

 touches the one point which is necessary before all else to improve, if 

 not to perfect, the practice of electrical engineering, so far as this is 

 aimed against the destructive powers of lightning. The broad pi'in- 

 ciples upon which the engineer prosecutes his work are happily such 

 as can be referred to actual experiments carried out by the artificial 

 apparatus of the electrician. But there still remain some incidental 

 questions, such as the influence of surface, extent, and form in con- 

 ductors, the relation of conductivity to tenacity, the area of protec- 

 tion, and the maximum effect of lightning, which can not be settled 

 in this way, and which require an appeal to the larger operations of 

 Nature. This, however, concerns opportunities which can not be 

 arranged at will. The method of the appeal must of necessity be ob- 

 servational rather than experimental. It proceeds upon the lines of 

 close watching and systematic record. Observations where the great 

 operations of Nature are concerned are utterly worthless unless they 

 are made with scientific insight and precision. The plan of investiga- 

 tion that has to be pursued is therefore to collect an exact account of 

 all accidents that occur, and to arrange a system of organization which 

 enables all such chance opportunities to be seized upon and improved 

 by an immediate investigation of concomitant conditions and circum- 

 stances. This method of study also must be followed up by patient 

 persistence for a considerable length of time, seeing that accidents 

 from lightning occur at uncertain intervals, and that they are scattered 

 capriciously over the greater part of the surface of the earth. It is for 

 this reason, essentially, that a Lightning-Rod Committee needs to sit in 

 permanence. 



