ELECTRICITY OF INDUCTION. 467 



precise metliods and uuder favorable circum stances, I feel at liberty to 

 deny the fr^e negative electricity of a serene sky, and also the existence 

 of clouds endowed, as a property, with this electricity, maintaining that 

 the negative electricity only manifests itself with the falling of the rain, 

 hail, or snow, through the effect of the influence of the positive electricity, 

 which is copiously developed on the resolution of the clouds into water. 

 1 deem it useless to explain how negative electricity may also be pres- 

 ent when rain falls on the place of the observations, for this indicates 

 another more iutense rain which is proceeding at a certain distance.'-* 



The Eev. Padre A. Secchi shows that he holds the same doctrine, for 

 he says : 



"In regard to tlie foct asserted by Professor Palmieri that nega- 

 tive electricity is not present in a serene state of the sky, except in the 

 case of rain actually falling on the spot, or at least at some distance off 

 and in view of the horizon, I have found it to be constantly veriiied." 



He also recognizes a primary negative zone, which attends a storm 

 through the etfect of induction.t 



The opinion of Professor Palmieri, thus sustained by Eev. Padre A. 

 Secchi, is wanting in i)oint of positive proof. It would be necessary, in 

 order to supply such proof, that an experimenter should be stationed at 

 the center where the cloud which is being resolved into rain is directly' 

 superincumbent, and should investigate the kind of electricity of the 

 falling shower; while other exxjerimenters should be placed around its 

 periphery', so as to form a ring, each of whom should exploie the 

 nature of the electricity of the air surrounding the dissolving cloud. 

 By a complete experiment like this, the x)robleui propounded by Pro- 

 fessor Palmieri might be solved. The rain falling at the center, endued 

 with positive electricity or with negative electricity, should be found to 

 have around it a circle of negative electricity or of positive electricity. 



I requested Padre A. Secchi to make this experiment in the environs of 

 Eome, but he assured me that it could not be carried into effect there 

 on account of the topographic difficulties of the hills which encompass 

 that city. aSTot being myself able to prosecute the exi)eriment on a 

 large scale in the Euganeau region and the circumjacent cities of 

 Yicenza, Lignano, Badia, Eovigo, and Padua, I limited my views to a 

 cabinet experiment, which, nevertheless, appears to me sufficient for the 

 solution of the proposed problem. I suspended to a thread of silk a 

 hollow sphere of brass, which I proceeded to electrify now positivelj^ 

 and again negatively. Arranging around it the wire of a straw electro- 

 meter and bringing it successively nearer to the electrified s[)here, I 



* Bolldino metcorolofjico dcJV Osscrvatorio del CoUcgio I^omano, Vol. II, No. 15, p. 113, 

 for the year 1863: Letter from Signor L. Palmieri, director of the Osservatorio Vcsuviano, 

 to Padre A. Secchi. 



\ Bollctino mettoroJofjico ddV OsseriYitorio del Collcgio Homano, Vol. II, No. 17, p. 129, 

 for 18G3 : Reflections of Professor Francesco Zantedeschi ou the article of Patlre k, 

 Secchi, entitled: Allic studii dl clcttridta atmosjpherka. 



