123 



for indemnity, which was refused, upon the plea that a tornado was 

 not a thunder gust (orage). The question having heen submitted to 

 Arago, it was by him referred to Peltier. 



Peltier, after due investigation, came to the conclusion that a tor- 

 nado is a modification of the thunder gust, in which, in lieu of passing 

 in the form of lightning, electricity passes through a cloud, acting as 

 a conductor between the terrestrial surface and the sky. It will be 

 perceived that this view of the subject differs but little from that 

 which, in a memoir in the transactions of the Society, had been pre- 

 sented by Dr. Hare, in the following language: — " A tornado is the 

 effect of an electrified blast of air, superseding the more usual means 

 of discharge between the earth and clouds, in the sparks and flashes 

 which we call lightning. I conceive that the effect of such a current 

 would be to counteract, within its sphere, the pressure of the atmos- 

 phere, and thus to enable this fluid, in obedience to its elasticity, to 

 rush into the rarer medium above." 



Dr. Hare went on to say, that the only difference arises from the 

 omission of the Parisian philosopher to call in the electricity of the air 

 in aid of the electrical forces, and his assigning to a cloud the agency 

 which Dr. Hare had attributed to a vertical blast of electrified air, min- 

 gled with every species of moveable matter coming within the grasp 

 of the meteor; and that it would seem, from a subsequent communi- 

 cation made by Peltier to the Institute, that he had so entirely misap- 

 prehended Dr. Hare's theory, as to ascribe to it deficiencies for which 

 it was not amenable, but which had existed in his own explanation, as 

 stated in his report. 



The fault of Dr. Hare's explanation was, according to him, " en 

 ne tenant pas compte des forces nouvelles que la premiere, (that is 

 to say, the electric attraction,) acquiert par le mouvement gyratoire 

 qui accompagne souvent la coulonne de nuages et d^eau qu'on ap- 

 pelle trombeP 



As the most appropriate refutation of this mistatement, Dr. Hare 

 stated that he would quote a paragraph from his Memoir. 



" When once a vertical current is established, and a vortex pro- 

 duced, I conceive that it may continue after the exciting cause may 

 have ceased. 



" The effect of a vortex in protecting a space about which it is 

 formed, from the pressure of the fluid in which it has been induced, 

 must be familiar to every observer. In fact, Franklin ascribed the 

 water spout to a whirlwind. 



