4G6 



METEOEOLOGY. 



cieut agreement, and at tlie same time show that these differences in- 

 crease from January till the month of July, and then diminish until 

 December, in which occurs the minimum of difference for the two in- 

 struments. 



In calculating- the evaporation by day and that by night for each 

 month, we have found the following numbers : 



Evaporation. 



Months. 



By day. 



Millimeters. 



January .. 

 February . 



March 



April 



Iilay 



Jane 



July 



August - - . 

 September 

 October... 

 November 

 December 



96 

 35 

 95 

 64 

 38 

 99 

 30 

 02 

 27 

 26 

 2.48 

 1.93 



By night. 



Millimeters. 



0.64 



0. 63 

 0.70 

 0.87 

 1.13 



1. 38 

 1.63 

 1.82 

 1.76 

 1.67 

 1.20 

 0.80 



Eatio. 



Millimeters. 



3.03 

 3. 73 

 4.21 

 4.18 

 3. 91 

 3. 62 

 3.25 

 2.76 

 2. 43 

 1.95 

 2.07 

 2.41 



Thus the greatest evaporation at night occurs in the month of August, 

 the least in February ; the ratio hetiveen that of day and night increases 

 from October to March, and then diminishes gradnaJly till October. 



From what we have thus been able to compile it would evident! j' seem 

 that for a complete study of the subject of evaporation it is indispens- 

 able to have two atmometers, one to be stationed with the other meteor- 

 ological instruments, and defended from the direct action of the wind 

 and rays of the sun, the other entirely free. For the latter jiurpose the 

 construction of the Gasparin atmometer is suited, for the former that of 

 Vivenot, though it might be expedient to give to this last greater dimen- 

 sions than those heretofore employed. 



ON THE ELECTRICITY OF INfll'CTIOX IN THE AEKIAL STRATA OF THE ATMO- 

 SPHERE WHICH, IN THE SHAPE OF A RING, SURROUND A CLOUD THAT 

 IS RESOLVING INTO RAIN, SNOW, OR HAIL. 



By Pkofessor Fk. Zantedeschi, 

 Of the Royal Venetian Institute of Sciences, Letters and Arts. 



[Extracted from Vol. XII, scries III, of the Transactions of the Institute.] 



Professor Luigi Palmieri states as follows: 



" Where rain is falling there must be present positive electricity, with 

 a zone or wave of negative electricity on every side, which zoue, in tem- 

 pestuous weather, may extend to a distance of thirty miles, especially in 

 summer. Upon this subject, after so many observations, conducted by 



