CONCERNING THUNDERSTORMS 



641 



full time had elapsed for the earth to reply, not least, the tracing of the river Amazon 



when the same peal of thunder rose up and its tributaries from a school atlas, 



which we were already accustomed to. to represent the lightning flash ! I leave 



And this thunder was in no way dimin- it to the reader to decide whether or not 



ished by the inter^•ening depth of dense the comparison is a good one, for actual 



cloud, which the waves of sound would have photographs of lightning flashes are re- 



to traverse. . . . The result was always produced further on, and special attention 



the same, and proved first throughout is called to the flash on page 643 



this afternoon 

 there was never 

 e ^' e n the s u s- 

 picion of an echo 

 from the cloud or 

 sky." 



Leaving the 

 subject of thunder, 

 attention may 

 now be directed 

 to perhaps the 

 most interesting 

 feature of thunder- 

 storms, namely, 

 lightning dis- 

 charges, which, as 

 I have previously 

 indicated, are no- 

 thing but ordinary 

 electric sparks on 

 a gigantic scale. 

 Most of us are 

 familiar with their 

 general appear- 

 ance. Their form 

 was. and even 

 now is, sometimes 

 described as " zig- 

 zag," but this is 

 quite erroneous, as many of my readers 

 are aware. In a large experience of watch- 

 ing flashes closely, I ha\'e never observed 

 a single instance of such a form, and 

 after an examination of several hundred 

 photographs I ha\'e never seen one that 

 exhibited this shape. 



Flashes of lightning, especially when 

 they are accompanied by branches or 

 ramifications, have very much the appear- 

 ance of a river and its tributaries, as 

 shown on maps. To illustrate what I 

 mean I ha\'e prepared the accompanying 

 illustration. 5sow this photograph is not 

 a flash of lightning taken with a camera 



"'hotOiri'aph by Dr. Locky^r. 



A TRACING OF THE RIVER AMAZON AND ITS 

 TRIBUTARIES TO REPRESENT A FLASH OF 

 LIGHTNING WITH RAMIFICATIONS. 



Curiously e n- 

 ough it is only, 

 roughly speaking, 

 within the last 

 t w e n t y-fi \- e or 

 thirty years that 

 the study of light- 

 n i n g has been 

 made \\' i t h the 

 photographic 

 camera. The ap- 

 plication of the 

 sensitive plate has, 

 however, cleared 

 up many old 

 fallacies, while at 

 the same time it 

 has taught us 

 many things con- 

 cerning hghtning 

 flashes which were 

 unknown before. 

 With such fleet- 

 ing obj ects as these 

 discharges the eye 

 is very apt to be 

 deceived, and it is 

 just in such in- 

 stances that the 

 camera becomes invaluable. 



In fact, the enjoyment of a thunder- 

 storm is considerably enhanced by making 

 use of a camera, or several if one is 

 fortunate to have more than one. One 

 is able then to supplement camera with 

 eye work, and obtain very useful results. 

 Space does not permit me to refer, 

 even briefly, to the many points of interest 

 that this instrument has opened up, but 

 some of the more important of them may 

 be mentioned. 



In the first place, the general form of 

 the lightning flash was accurately recorded, 

 showing that the flash was usually of a 



but a composite picture made up dexter- wavy (not zigzag) nature, and that some 



ously by means of a piece of cut paper to times it had branches and sometunes 



represent a landscape, the use of cotton none at all. Se\-eral specimens of these 



wool to give cloud effect, and last, but t3-pes will be seen in the accompan>-ing 



