300 C. Ray Woods.— On some [Aug. 29. 



looping of the flash. The Committee goes on to point out, what is 

 also plainly evident in the beaded appearance in the photographs 

 which I have taken myself, that it is evidently due to the flash taking 

 at times a course to and from the observer and giving a longer 

 exposure to these spots. 



6. Ribbon Lufhtning. " Nearly one-sixth of the photos received by 

 the Society show flashes exhibiting more or less of a ribbonlike form^ 

 One edge of the ribbon is usually much whiter and firmer than the 

 other." The Committee points out that this form is probably due to 

 double image formed by internal reflections of doublet lenses. This 

 defect then, if it is only a defect, is visible in my own photos, more 

 particularly in those parts of the flash nearest the edges of the plate. 

 My experiments were made with a doublet lens, as at the time they 

 were taken the report I quote was not published and 1 was not 

 aware that a single lens gave the best results. 



Of these various forms I pass round illustration and draw attention - 

 to the diagrams on the wall which are roughly copied from specimens 

 issued with the report. 



The beaded appearance in my plates I have already drawn atten- 

 tion to. Apart from this they might be classed as sinuous, meander- 

 ing, or as ramified, as they partake more or less of all three 

 characters. I have already mentioned the clouded condition of the 

 sky and T need not add that clouds must necessarily be present where 

 lightning discharges take place. The Committee have singularly 

 enough overlooked this, the simplest explanation of the variation in* 

 thickness of a flash. Cannot the cutting off of parts of a flash by 

 cloud, and modification of the other parts of absorption through cloud, . 

 explain some of these forms assumed by lightning flashes .^ 



Let me draw your attention to two diagrams roughly copied from* 

 photographs of the electric spark taken by Mr. Trueman Wood, of the 

 Society of Arts, with a large induction coil. 



Here is a single spark which obviously corresponds with Class 1 or 

 Stream Lightning. The next is the result of six successive sparks > 

 impressed on the plate. By covering portions of this photograph we 

 can get tolerably near approaches to the sinuous, ramified, and^ 

 meandering types. The beaded type, which is readily explained, has- 

 been obtained by Mr. Wimshurst with a large electrical influence 



machine. 



In a thunderstorm, as terminals of the natural electric machine we^ 

 have not one only but sometimes many points of discharge, in the- 



