470 METEOROLOGY. 



euabled by all tbose causes to note the passage from one phase to tlie 

 other. Siicli is the origin of every phenojicnou previously observed. 

 After having established this law hj many personal observations, I did 

 not tiiil to seek for its corroboration in the records of tlie observations of 

 others; and many facts mentioned by Beccaria seemed to me derived 

 from that law, which is otherwise corroborated in a description of a fall 

 of hail observed by Oward. Quetelet, upon hearing of this law, exam- 

 iued the records of his own observations, and found it corroborated by 

 them; and he then proclaimed it also, taking my observations into ac- 

 count, but not giving me clearly the priority of discovery that undoubt- 

 edly belonged to me. Afterward others confirmed said law, which I 

 never fiiiled to verify whenever opportunity offered, the best conditions 

 being to have a very extensive horizon and a rain or storm commencing 

 at a considerable distance from the observer, approaching him with the 

 v,iud, and then leaving him behind. These are, in fact, the onlj' condi- 

 tions in which it is possible to verify the truth of the above-mentioned 

 law. 



On the 20th of September, ISOS, on or about 11 o'clock a. m., there 

 appeared above the sea, in a westerly direction, somewhere beyond the 

 Ponzie Islands, a cloud of very small dimensions. Suspecting a storm, 

 I used the apparatus with movable conductor, and noticed a strongly 

 positive tension, indicating a distant rain ; and suspending the con- 

 ductor in an elevated position, the oscillations of the gold plates of Boli- 

 nenberger's electroscope indicated lightning. The wind was very weak 

 and coming from southwest, bringing the storm toward the observatory. 



At noon the tension became negative, and after a few moments, dur- 

 ing vrhich it was null, and when already could be heard the thunder-claps 

 of the approaching storm, the negative tension increased so as to emit 

 sparks ; thunder was heard more distinctly, and rain was seen falling 

 on the Campania. At 1 o'clock p. m. rain was falling upon the observa- 

 tory, and the tension, passing through 0, became positive. At 3 p. m. 

 rain had ceased to fall on the observatory, but was falling over Castel- 

 lamare, giving again a strong negative tension. Over the Mounts of 

 Castellamare it ceased to rain, and positive electricity returned, but with 

 a weak tension of 15°. Had the storm kept on its primary course east 

 of the observatory, there should have been a strong positive tension 

 ( -f co). In this case, therefore, the last phase alone failed to be observed. 



Whoever found himself in elevated places, or upon the open sea, must 

 have often noticed two or more rains, each distinct from the other, fall- 

 ing with small intervals between them ; and this explains why apparent 

 exceptions are often recorded against tlie universality of the law. Let 

 us suppose, for instance, that on the spot where is the observer a rain is 

 fallmg, while another, stronger, falls at some distance ; then it becomes 

 evident that, if positive and negative electricity were to be obtained 

 from the first stronger than from the second, with the rain falling upon 

 the observatory, there should be in it negative electricity. And this is 



