498 S. H. Freeman—Electrification by Evaporation. 
ese from other ae and in this way give rise to 
secondary changes.* 
Pa rtial presence of Oxygen.—W hen wee of Helianthus 
e 
posed to a current of air made up of a mixture of one-fifth air 
and fourth-fifths nydrogen, a comparison of the excreted car- 
acid in both cases shows no difference whatever. Sufhi- 
cient yee is heb in sey mixture to supply all demands 
made by the plants. When, however, the expired carbonic 
acid in the depen kt of ees placed ‘first in air, and then 
a mixture of 45 air and $4 hydrogen, is compared, one finds he 
septs aac g greater during respiration in air. Thus a trifle 
Ta iibingen, Wirtemberg, April, 1882. 
Arr. L.— id Question of Electrification by Evaporation ; by 
S. H. Freeman, Fellow in Physics in Johns Hopkins Uni- 
versity, Baltimore, Md. 
Ir has been very commonly believed that evaporation is an 
important source of atmospheric electricity. So far as this be- 
lief has an experimental basis, it is sy be found in the researches. 
of Pouillet,t and of Tait and Wanklyn.§ In comparison with 
their work the experiments of Volta, Saussure and others are of 
little value. As the result of an elaborate series of experiments. 
ouillet came to the following conclusions : 
1. Simple changes of state never give the least sign of elec- 
trification. 
= ao ride mae nur, dass i in beiden Fallen ag oe aeiembonge des Kohlen 
r dies 
gen, An 
ee von Sauerstoff aus anderweitigen Verbindu ungen eben die Veranlas- 
zu sekundiiren Prozessen werden. Pfeffer, Planzenphysiologie, Bd, J, 1881, 
ethods of analysis which A it ce cone the detection of one- 
