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A WEEKLY NEWSPAPER OF ALL THE ARTS AND SCIENCES. 



Eighth Year. 

 Vol. XV. No. 88 



NEW YOEK, Juke 13, 1890. 



Single Copies, Ten Cents. 

 $3.50 Per Year, in Advance. 



THE TORNADO: THEORIES; OBJECTIONS. 



It is somewhat difficult to give an adequate idea of the 

 development of theories or pure speculations in this subject. 

 Owing to the complex nature of the phenomenon, and the 

 well-nigh utter lack of observations in the region of tornado- 

 formation, the earlier views were more or less crude, and 

 in some particulars have been slightly modified as broader 

 and more comprehensive generalizations have been made. 

 We shall be surprised, however, to find, on a careful study, 

 how few changes tlie last fifty years have wrought. The origi- 

 nal and essential ideas of tornado-generation and of sources 

 of its power remain to-day as first propounded by Espy in 

 1840. Since his day. Professor Ferrel has been the most 

 prominent exponent and amplifier of his views; and, with 

 very few exceptions, theorists have followed Ferrel down to 

 the present time. In many respects it would be a great advan- 

 tage if one could give an impartial and trustworthy summing- 

 up of the views of these men, and could bring out distinctly 

 their gradual development. It will be far safer, however, 

 since there are scores of students to-day who call in question 

 many of these deductions, to give, as far as possible, an un- 

 biassed resume of these theories in the exact words of their 

 defenders, and thus enable any one for himself to examine 

 their adequacy for explaining the phenomena as they are 

 manifested before our eyes. 



Espy's Views. 

 It is not a little remarkable that the first investigator of 

 any note in this field based all his theories on direct experi- 

 ment in the laboratory. All theorists since Espy's day have 

 not considered that there was any need of propounding any 

 of these questions to Nature herself, but have contented 

 themselves with the assumptions and necessarily imperfect 

 and crude results obtained by the Qrst experimenter. This 

 is the more remarkable when we consider the extreme grav- 

 ity of the subject, and the methods employed in all other 

 sciences, except meteorology, to establish upon a firm and 

 impregnable basis such profound and far-reaching theories. 

 Espy's few and simple experiments at almost the very dawn 

 of this science have never been repeated by theorists as far 

 as the writer is aware. This one fact would seem of the ex- 

 tremest importance; and . when we see, further, that even 

 Espy himself was entirely unable to account for some of the 

 anomalies in these very experiments, we can but feel the ex- 

 treme necessity of further light. This feeling has borne 

 fruit in other countries, as is sliown by the diligence recently 

 manifested in researches with rapidly revolving fans, which 

 cause a supposed simulation of the phenomena in nature. 

 While we can never hope to completely unravel the myste- 



ries hidden in our storms until we question Nature herself in 

 her own great laboratory, yet we can insist upon an examina- 

 tion of the original researches used as a basis for these theo- 

 ries, and demand a determination of their adequacy upon 

 which to base the completer speculations of modern times. 

 Nephelescope. 

 The apparatus Espy used he called a "cloud-examiner." 

 It consisted of a glass cylindrical vessel, having attached to 

 it by an opening at the top (1) a condensing syringe, by 

 which the air in the vessel could be compressed ; (3) a glass 

 (J-tube half full of mercury, by which the amount of com- 

 pression could be measured ; (3) a stop-cock between the 

 syringe and the vessel. "After the instrument is charged, 

 the stop-cock is turned, and the pump removed. When the 

 air within acquires the temperature of the air without, a 

 measure is carefully applied to the barometer gauge to ascer- 

 tain how much higher the mercury stands in the outer leg 

 than in the inner; the stop-cock is then turned, and the air 

 permitted to escape; and at the moment of equilibrium the 

 stop cock is closed again. Now, as the cock is closed at the 

 moment the greatest cold is produced by expansion, the mer- 

 cury in the outer leg will begin to ascend, and that in the 

 inner leg to descend, because the air within receives heat 

 from without; and the difPerence of level, being measured 

 as before, will indicate the number of degrees cooled by a 

 given expansion. When dry air is used in the experiment, 

 the temperature is reduced about twice as much as when 

 moist air is used, on account of latent caloric evolved in the 

 latter case by the formation of cloud which is plainly visi- 

 ble." Saturation of the air was attempted by placing a little 

 water in the bottom of the vessel. The amount of com- 

 pression varied from two to twenty-five inches; that is, the 

 gauge indicated an increased pressure inside the vessel, 

 amounting in some instances to nearly that of an atmos- 

 phere. These experiments were certainly unique; and, 

 while we shall see that they by no means prove Espy's the- 

 ory, yet they must be regarded as a step in the right direc- 

 tion, and a faithful efPort to elucidate a most complex prob- 

 lem. As all clouds in these experiments were formed by ex- 

 pansion of compressed air, it is not a little remarkable to 

 read the following as Espy's method of forming clouds, given 

 by Professor Ferrel: "As Espy with a few strokes of the 

 handle of an air-pump produced a cloud in the receiver from 

 the expansion and cooling of the moist air within, so nature, 

 by means of a whirl in the open atmosphere, produces a cloud 

 in the vortex of a tornado, from the expansion and cooling 

 of the air there, on account of the partial vacuum caused by 

 the centrifugal force of the gyrations." It is entirely prob- 

 able that the rapidity of this expansion and consequent cool- 



