October 23, 1890] 



NATURE 



613 



points on which Prof. Hazen's views are in dissonance with 

 those of most other writers who have treated of tornadoes. 

 Among others, he assures us (p. 57), that " the evidence 

 for [their] gyrations is exceedingly contradictory, and the 

 weight of evidence is overwhelmingly against them " ; 

 that (p. 52) it is impossible that warm south wind under- 

 runs that which is cooler from the north, " for the denser 

 must always be beneath the lighter" ; and (p. 59) that it 

 seems impossible to ascribe the progressive movement of 

 the tornado to the drift of the upper current, " because it 

 moves with a velocity double that of the general storm." 

 Those who are curious to see the further arguments by 

 which these theses are supported must be referred to the 

 work itself. We have yet to notice briefly the alternative 

 views advocated by the author. 



The late Dr. Percy used to relate that, in his early days, 

 when the iron would not " come to nature " in the Stafford- 

 shire puddling furnaces, the workmen were accustomed 

 to ascribe its perversity to the presence of sulphur in the 

 charge. In still more remote times, the potentate in 

 whose realm that element is supposed to be somewhat 

 abundant, or his agents, would assuredly have been held 

 responsible for what was amiss. But thirty years ago the 

 march of science had brought in other ideas, and the 

 approved explanation of any otherwise unaccountable 

 difficulty of the kind was that electricity had something 

 to do with it. Even at the present day this mysterious 

 agency is the favourite resource of puzzled tyros in physi- 

 cal reasoning, but we should hardly have expected to find 

 it seriously put forward in all its familiar vagueness by an 

 author whose official designation is that quoted above 

 from the title-page of his work. That such, however, is 

 the case stands in evidence in the following extracts, 

 which we give as fully as our space will admit of, lest 

 we should fail to do their author justice : — 



" It is very difficult to believe that electricity has nothing 

 to do with our thunder-storms, and is merely a result and 

 never a cause. . . . Our thunder-storms seem to show an 

 enormous storehouse of electricity at five thousand or six 

 thousand feet above the earth ; at least electricity seems 

 to be concentrated there over thousands of square miles 

 during thunder-storm action. We are taught that elec- 

 tricity forms a sort of dual condition, or the electric field 

 is a double one. May not this electric field draw on the 

 sun for its energy ? . . . Why may not the sun's electricity, 

 oftentimes observed by its direct effect on our magnetic 

 instruments, and, more often still, indirectly in our auroras, 

 be intercepted by a peculiar condition of the atmosphere 

 or of the earth below, and thus be concentrated in 

 particular localities ? " 



This may, perhaps, appear somewhat vague as an 

 alternative theory of storm generation ; in one particular, 

 however, viz. the accumulation in the storm-cloud of 

 the enormous quantities of water precipitated in cloud- 

 bursts, the modus operandi is more fully explained. In 

 Prof Hazen's opinion, it would seem that electricity per- 

 forms a part in the atmosphere somewhat analogous to 

 that of Clerk Maxwell's hypothetical demons, and which 

 is described as follows : — 



"Is it inconceivable that we have to deal here with a 

 negative electric field, which draws to itself with great 

 velocity particles of moisture from regions perhaps for 

 one hundred miles about, when suddenly, upon a dis- 

 charge of electricity, the potential upon the particles is 



NO. 1095, ^'OL. 42] 



diminished, and they unite in great abundance and form 

 rain-drops ? " 



This remarkable speculation, it is considered, receives 

 support from a novel experiment described as follows : — 



" A Holz machine was run for fifteen minutes in a 

 rather large room ; and most careful measurements of 

 the amount of moisture at the machine and at a point 

 twenty feet away, before and after the machine was in 

 action, showed an increase at the machine. When we 

 consider that it was impossible to measure the moisture 

 contents just at the plate of the machine, and also what 

 an extremely slight charge could by any possibility enter 

 the air from the machine, we can but be surprised that 

 any effect at all was observed." 



Without imitating King Charles the Second's scepti- 

 cism in the matter of the fish's weight in water and out 

 of water, but accepting Prof Hazen's statement of the 

 results as he gives them, we may still inquire whether 

 the operators who worked the Holz machine continu- 

 ously for fifteen minutes did not exhale a considerable 

 quantity of water vapour in the neighbourhood of the 

 machine. Perhaps they even perspired freely with their 

 exertion. In any case the foundation seems hardly 

 adequate for the superstructure. 



Had this book appeared under a less known name, 

 and were it not for the official position of the writer, 

 we should scarcely have deemed it desirable to 

 notice it at such length. A really searching, intelligent 

 criticism of Ferrel's theory, by one who has exceptional 

 advantages for ascertaining the facts of observation, 

 would have been welcome ; for, symmetrical as that 

 theory is, it is still mainly deductive, and there are many 

 points in it, and these not the least important, which still 

 lack confirmation. But we cannot attach much weight 

 to the objections raised by Prof Hazen. They seem to 

 betray a strange misconception of the physical processes 

 which he condemns in such uncompromising terms ; and 

 where his arguments turn on the facts of observation, we 

 must decline to accept his sweeping denials, in the face 

 of the positive testimony of numerous, not incompetent, 

 observers. In some cases, indeed, we might adduce our 

 own personal experience of phenomena which are declared 

 by him to be improbable or impossible. Such are, for 

 instance, the superposition of dry northerly above warm 

 and moist southerly currents, and the spiral movement 

 of the air in dust whirls, which, on a miniature scale, 

 represent that of the tornado. 



Again, Prof Hazen's argument that the rise of pressure 

 beneath a thunder-storm is sometimes observed in storms 

 that are rainless, and therefore cannot be due to the cool- 

 ing of the air by the rain, or to its downward pressure as 

 it falls, is rendered of little weight by the fact that this 

 occurs only when the lowest strata of the atmosphere 

 are very dry. In the recently published " Climates and 

 Weather of India," it is stated that " a complete transition 

 may be traced between [the rainless dust-storms of Upper 

 India] and the north-westers of Bengal, which are ac- 

 companied by heavy rain." In the latter province "the 

 dust-storm is. as a general rule, only the first stage of c 

 north-wester." It is attended with a sudden rise of pres- 

 sure, and "is followed by heavy rain and sometimes 

 hail," and though the dust-storms of the former are 

 occasionally, though perhaps rarely, quite rainless, 



