432. SS. H. Freeman—Electrification by Evaporation. 
depth is meant the depth of the layer of water over the whole 
area of the cloud, were all its vapor condensed to the liquid 
tate. 
Let J=this depth in c.m. fora cloud of area A and height a. 
Let V and C=respectively the potential and capacity of the 
cloud. 
Let g=the charge per gram of water. 
Then “ 
C 
4 AQ 
But from Sir Wm. Thomson’s experiments V=130a,* and 
by re or atnae formula for a condenser of horizontal wae 
A 
~ 47a 
Now in the experime 
Let d=the , ‘biained by insulating for ¢ minutes, 
and apparently due vapor 
Let D=the iedlasion shared iin a Daniell’s cell. 
<o W=weight in grams of Jiquid evaporated in T minutes. 
v and c=potential and capacity of evaporating dish and 
its Deniers 
But c=65 c.m. as stated above; and »=0-008745 in electro- 
static units according to Sir Wm. Thomson’s measurements. 
a at 
. d=43 Ta 
experiments. 
in terms of the original measurements in the 
I. Zable showing results of earlier series. 
[eg See | 5 © ; 
| oun} oeg | ci | oe | S| | BES 
Liquid. | SSE | BES | scale | scale | 55 mine Win | A (See 
| eo | ap pike —— ~& | utes. | 6Fams.| in cm. | 35° 
a 2 & = ons. e | Pie) 
o | | n 
Distilled water 4°12 | 4°60 |+0°48) 42°02| 5 43 jae | 630 + 
Distilled water 4:82 | 4°35 0°49 42°05} 5 43 | 0°49 210 — 
Distilled water 3°95 | 4°50 |+0°55 | 41°55) 5 37 | 0°54 237 + . 
Distilled water 2°48 | 2°33 |—0°15 | 42°00| 5 41 | 0°80 | 1170 _ 
Solution NaCl 6°70¢| 468 |—2°02| 41°75] 6 55 | 029] 24] — 
Solution NaCl 3.47 | 440 |+0°93 41°50) 5 54 | 0°48 85 | + 
Solution NaCl 3°10 | 3°94 14+0°84, 42°20] 5 39 | O70! 194 + 
* Papers on Electricity an pea Cort 259, 
+ Pancieo n Electricity and Magnetism, p. 245. 
t hecaaghnat this series t was an a eae stenagnee" 7 breaking con- 
tact, which was several times r than otal deflection during the 
i ion. The pet therefore is al much less ate ‘Gan any of the 
others in which the instantaneous deflection was never more than 071 of a 
division, 
