838 
been weakened in this way might regain 
their strength if the mites and fungi could 
be kept down; but those which are natu- 
rally weak cannot be made strong. During 
the time plants are being forced they may 
also be weakened by overwatering and con- 
sequent asphyxiation of the roots, or by 
allowing the roots to become too dry and 
then overwatering. The foliage of such 
plants may be free from spots and distor- 
tions, but usually the leaves are badly dis- 
eased. The spotting and distortion of the 
foliage is often due to the direct attacks of 
several genera and species of aphides and 
of the young of the bulb mite; to the in- 
jection of water into the young leaves in 
watering or syringing, and to the presence 
of water between the young leaves of plants 
having soft foliage. The injuries from the 
attacks of organisms are always more severe 
in the susceptible or naturally weakened 
bulbs.” 
No single course of treatment can be 
recommended to help this trouble. Care- 
ful selection of the bulbs, rotation of crops, 
avoidance of premature cutting of the 
stems or digging of the bulbs, the use of 
aerated soil, care in watering, the careful 
destruction of aphides and mites and the 
use of chemical fertilizers, instead of those 
derived from animal excrement, are recom- 
mended as likely to materially check the 
disease. 
CHARLES EH. Bessey. 
UNIVERSITY OF NEBRASKA. 
NOTES ON INORGANIC CHEMISTRY. 
A RECENT number of the Zeitschrift fir 
anorganische Chenie contains a review of the 
recent work on the genesis of petroleum and 
other natural hydrocarbons. Engler’s hy- 
pothesis is that petroleum is formed by the 
distillation of animal fats at high pressure. 
Lobry. de Bruyn has described a demon- 
stration of this method of formation as a 
simple laboratory experiment. Heusler 
SCIENCE. 
[N. S. Vou. VI. No. 153. 
calls attention to the fact that Engler’s dis- 
tillate contains a considerable quantity of 
unsaturated hydrocarbons, which is not 
the case with petroleum. By treatment 
with aluminum chlorid these hydrocarbons 
are changed into a high-boiling lubricating 
oil; hence it is probable that petroleum 
formation took place in two stages, the first 
distillate being changed by metallic chlorids 
into petroleum. According to Ochsenius, 
petroleum was formed from plant and 
animal remains by heat and pressure 
under the influence of the salts derived 
from sea water. On the other hand, Mois- 
san finds in his work on the metallic 
carbids, a confirmation of the theory first 
proposed by Mendeleef, that petroleum 
originates from the action of water on metal- 
lie carbids in the interior of the earth. 
Uranium carbid, for example, yields with 
water both solid and liquid hydrocarbons. 
These are, indeed, in part unsaturated, but 
ata higher temperature saturated hydro- 
carbons might be formed from them by the 
action of hydrogen, which is often evolved 
from carbids by water. Aluminum carbid 
and glucinum carbid, indeed, give with water 
pure methane (marsh gas). Viola believes 
that the asphalt and the petroleum of Cas- 
tro de Volci, near Rome, in Eocene lime- 
stone and sandstone is of intratelluric 
origin, and has been distilled from great 
depths. The region shows decided evidence 
of voleanic phenomena. On the other hand, 
van Werweke holds that the petroleum of 
Pechelbronn, in Lower Alsace, has origi- 
nated in Tertiary strata and has not come 
from below. 
In a polemic article in the Zeitschrift fiir 
angewandte Chemie, D. Holde claims that the 
theory that petroleum has originated from 
animal remains should be known as the 
Engler-Ho6fer theory, Hofer having first pro- 
posed the theory in 1888 in his‘ Das Erdol 
und seine Verwandte,’ and Engler having 
