December 17, 1909] 



SCIENCE 



869 



light from wet or polished surfaces to 

 traverse the plate in an irregular course. 

 They are then only records of the inadver- 

 tence of the lightning photographer. In 

 one instance the effect was so curious that 

 it was several years before the true ex- 

 planation was found. In that case there 

 were two wavy contorted sti'eaks of per- 

 fectly parallel and of similar outline, but 

 unequal in intensity, rising each from a 

 rail of a single track railway, and appar- 

 ently terminating in the air fifteen or 

 twenty feet above the tracks. They were 

 finally traced to a moving camera, and a 

 reflection from the wet and polished rail 

 surfaces of the light of an arc lamp lo- 

 cated outside the field of view. It required 

 a visit to the place itself to enable this con- 

 clusion to be reached. The particular 

 beaded streaks or lines of dots were traced 

 to the fact that the arc lamps causing them 

 were operated by alternating currents 

 which naturally give light interrupted at 

 the zero of cui'rent; one hundred and 

 twenty times per second being the usual 

 rate. All this emphasizes the need of care 

 and wholesome scrutiny or even skepticism 

 before reaching a conclusion in such cases. 

 Is bead lightning, which has at times 

 been described as observed visually, a real- 

 ity? If it is it appears to be even rarer 

 than the globular variety. Perhaps it is a 

 string of globules; a variety of globular 

 lightning. But we can not make assump- 

 tions. As in the case of globular lightning 

 there is some testimony, which can not be 

 wholly disregarded, tending to show that a 

 form of discharge resembling a string of 

 beads can actually exist. An account of 

 an instance was given me within one hour 

 after the occurrence itself. The witness 

 was kno-noi to me as perfectly reliable. 

 The appearance was described as a festoon 

 of finely colored oval beads hung as it were 

 from one part of cloud to another, and as 

 persisting for some seconds while gradually 



fading awaj'. The opposite ends of each 

 bead were said to be different in color. It 

 was seen during an afternoon thunder- 

 storm and spoken of as very beautiful, and 

 altogether different from the usual zigzag 

 flash. 



If I have dwelt upon these exceptional 

 appearances at some length it is because 

 they seem to show that in electricity there 

 is much yet to learn and abundant oppor- 

 tunity for future investigation. It is cer- 

 tainly literally true that, in the language 

 of Shakespeare, "There are more things 

 in Heaven and earth, Horatio, than are 

 dreamt of in your philosophy. ' ' Such work 

 belongs to the science of physics, now recog- 

 nized as fundamental in all study of na- 

 ture's processes. In electrical engineering, 

 which is in reality an art based upon ap- 

 plied physics, the subject of lightning pro- 

 tection has always been one of considerable 

 if not vital importance. Just as a light- 

 ning discharge from a cloud clears up a 

 path for other discharges to follow, so in 

 electric undertakings it opens up paths for 

 the escape of the electricity we are sending 

 out to do the work intended, such as for 

 lighting, power or other use. In the 

 past, disablement of machinery in electric 

 stations has not been rare. The recent 

 growth of long-distance transmission in- 

 volving hundreds of miles of wire carried 

 on poles across country, over hills and 

 through valleys, has set new problems of 

 protection, and called for renewed activity 

 in providing means for rendering the lines 

 and apparatus immune to the baneful ef- 

 fects of electric storms. Judging the 

 future by the past, we may conclude that, 

 whatever difficulties of the kind arise, in 

 the great future extensions of such engi- 

 neering work, science and invention will 

 provide resources ample for the needs, 

 and the rapid advance will be continued 

 unchecked. 



Elihu Thomson 



