Knowledgfe & Scientific News 



A MONTHLY JOURNAL OF SCIENCE. 



Conducted by MAJOR B. BADEN-POWELL, F.R.A.S., and E. S. GREW, M.A. 



Vol. IV. No. i. 



[new series.] JANUARY, 1907. 



[stationers' Hall 



.] 



SIXPENCE NET. 



CONTENTS.— See page V. 



Lightning Flashes from Earth 

 to Cloud. 



By William J. S. Lockver, M.A., Ph.D., F.R.A.S, 



(Continued fyom page 601, Vol. III.) 



The second photograph of an upward discharge, to 

 which mention above has been made, and which is here 

 illustrated in Fig. 5, was taken by Mr. James Craik 

 when he was at Heme Bay some years ago. Here we 

 see both the earth and cloud ends of the flashes, and 

 the ramifications are in both instances directed 

 upwards. 



In this photograph we have a unique example, so far 

 as I am acquainted, of two upward flashes photo- 

 graphed on one plate. The third and last photograph, 

 which, 1 believe, represents an earth-to-cloud flash, is 

 that illustrated in Fig. 6. For this photograph I am 

 indebted to Mr. J. F. Xewman, who secured this fine 

 ramified flash at Berkhamsted in July, 1904. This dis- 

 charge has everv appearance of being directed upwards 

 for the intensities of the three ramifications diminish 

 rapidly in the upper portions of the illustration. If the 

 flash were a perspective effect, the branches would 

 most probably be relatively more intense than they are 

 in the photograph. 



The above-mentioned photographs give us sufficient 

 evidence to indicate that it is extremely likely that 

 lightning flashes not only pass from the clouds to the 

 earth, but that they sometimes take the reverse direc- 

 tion. Certainly more photographs must be secured be- 

 fore this question can be considered settled once and 

 for all, and herein lies a piece of work that can be at- 

 tempted by anyone who has even a small camera at his 

 disposal. 



.4nother point that requires investigation is this. It 

 has often been stated that a lightning flash is of an 

 oscillatory character; that is, is composed of a series of 

 discharges, which go back and forth from earth to 

 cloud and from cloud to earth a number of times along 

 the same track. 



Thus, to take one instance, in an account of a pecu- 

 liar flash of lightning which Prof. Kayser, of Bonn, 

 Germany, described in \'ol. XL\TII. of the " Sitz. der 

 Kon. Preuss. .\kad. der Wissenschaften zu Berlin," he 

 wrote : — 



"There remains a fourth and quite satisfactorv ex- 

 planation, that we have here to do with an oscillating 

 discharge, in which flashes in opposite directions take 

 place in very close proxitnily to each other. Thus the 

 first flash on its way from cloud to earth would leave 

 behind it a channel of heated air; the next discharge 

 from the earth to the cloud would use the same path 

 which would still be in existence, only moved slightly 

 by the wind, &:c. . . . That 'such oscillating 

 lightning discharges occur has been observed manv 



Fig. 5. — Two earih-to-cloud discharges. Heme Bay. 



^hoio by Mr. James CraiX*. 



