Intelligence and Miscellaneous Articles. 223 



ON ELECTRICAL HEAT. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 In the Philosophical Magazine, vol. xii. p. 553, Sir W, Snow- 

 Harris has continued his opposition to an established law of electrical 

 heat, without, as is necessary, describing minutely the experiments 

 which he considers irreconcileable with that law. It is therefore 

 impossible to assign a reason for the remarkable result which his 

 experiment with two Leyden jars of different sizes led to. If Sir 

 William did really, as he asserts, charge the two jars with the same 

 amount of electricity, and all other conditions in the two jars were 

 identical, the small jar would undoubtedly on its discharge have 

 caused a stronger heating effect of the wire than the large jar. At 

 the same time the theory of the Leyden jar teaches that this expe- 

 riment can by no means serve as an accurate test of the law in ques- 

 tion, and cannot be called a crucial experiment. May I be allowed 

 in conclusion to repeat a statement which is not expressed with suf- 

 ficient clearness in my last letter } I request the reader not to con- 

 sider objections to my researches as well founded because I leave 

 them unanswered ; I pass over objections which are based upon a 

 misconception of my statements, and are easily corrected. 

 1 have the honour to be. Gentlemen, 



„ ,. Yours truly, 



Berhn, Jan. 20, 1856. •' p_ j^jj,gg 



ON THE SPIRALITY OF MOTION IN WHIRLWINDS AND TORNADOES. 

 BY W'. C. REDFIELD*. 



1. An aggregated spiral movement, around a smaller axial space, 

 constitutes the esential portion of whirlwinds and tornadoes. 



2. The course of the sjiiral rotation, whether to the right or left, 

 is one and the same in this respect throughout the entire whirlitio-' 

 body, so long as its integrity is preserved. But the oblique inclina"^ 

 tion which the spiral movement also has to the plane of the horizon, 

 is in opposite directions as regards the interior and exterior portions 

 of the revolving mass. Thus, in the outward portion of the whirl- 

 wind the tendency of this movement is obliquely downwards, when 

 the axis is vertical ; but in the interior portion, the inclination or 

 tendency of the spiral movement is upward. This fact explains the 

 ascensive effects which are observed in tornadoes and in more 

 diminutive whirlwinds. 



3. Owing to the increased pressure of the circumjacent air in 

 approaching the earth's surface, the normal course of the gradually 

 descending movement, in a symmetric whirlwind, is that of an 

 involuted or closing spiral ; while the course of the interior ascending 

 movement of rotation is that of an evolved or opening spiral. Hence, 

 the horizontal areas of the higher portions of the whirl exceed greatly 

 those of its lower portions. 



4. The area of the ascending spiral movement in the vortex, as it 

 leaves the earth's surface, is by far the smallest portion of the 



• Read before the American Association at Albany, Aug. 26, 1856. 



