458 
“The Forests of Oregon” (Bull. I., Oregon 
State Board of Forestry, 1911), by Professor 
G. W. Peavy, and the “ First Annual Report 
of the State Forester” of Oregon (1912), by 
F. A. Elliott, indicate the state of mind of 
the people of the northwest in regard to the 
conservation of their forests. 
One of the best of recent publications on 
trees is “ New England Trees in Winter,” by 
Professors Blakeslee and Jarvis, of the Storrs 
Agricultural Experiment Station (Bull. 69, 
1911). After a helpful introduction, by 
means of keys the student is led to the prin- 
cipal genera, where further keys lead him to 
the species, and last to full descriptions ac- 
companied by excellently selected photographs 
(in “ half tone”). We do not recall any better 
treatment of our trees than is to be found in 
this publication, nor anything approaching it 
in other station bulletins. The authors are 
to be congratulated upon the quality of the 
matter which they have presented, and the 
Station upon its wisdom in giving it publi- 
cation. 
Here may well be mentioned favorably E. 
R. Jackson’s “Forestry in Nature Study” 
(U. S. Dept. Agric. Farmers’ Bulletin, 468), 
which should be found in every public school 
in the country. Mr. Lamb’s “ Key to Com- 
mon Kinds of Trees” (p. 88) should prove 
helpful to many teachers who have somewhat 
hazy ideas as to the identity of the trees 
about them. Cuartes E. Brssry 
THE UNIVERSITY OF NEBRASKA 
SPECIAL ARTICLES 
THE ACCUMULATION OF OIL AND GAS IN SANDSTONE 
Ler two plates of glass be slightly inclined 
to each other and touching along one edge. 
Place by means of a pipette some petroleum 
and water between the plates. By manipula- 
tion of the plates, cause a bubble of air and 
oil to be enclosed within the water. It will be 
noticed that while the oil surrounds the air, 
much more than half of the oil will lie toward 
the thinner end of the combined bubble. This 
would, of course, naturally follow, since liquids 
are subject to capillarity and gases not. 
SCIENCE 
[N.S. Vou. KXXXV. No. 899 
Let us now consider the newly formed 
strata of marine or lagoon shales and sand- 
stones, which are potentially petroliferous. 
All the interstices will at first be filled with 
water. Assuming now that the petroleum and 
natural gas arise from chemical changes in 
included organic substances, principally in the 
shale, we have the following sequence of 
events. The gas that originates finds itself 
forced by the greater hold that the water has 
for the fine interstices to take a position in 
the largest near interstice. If this is more 
globular than tubular or flat, a bubble of gas 
will be thus imprisoned, otherwise it will move 
along till it reaches the largest lacuna. In 
other words, much of the gas will leave finer 
grained rocks for the coarser, and so produce 
an accumulation of gas in sandstone reser- 
voirs. Gas then is the first constituent to be 
forced into these reservoirs. 
But further, although petroleum has a 
lower capillarity constant, it has an extraor- 
dinary capacity of spreading along a surface 
between water and a gas. This is shown by 
the way oil will surround a bubble of air in 
water between two plates of glass. Therefore, 
in the movement of the gas bubble from the 
place of origin to the reservoir, each will carry 
with it a pellicle of oil, and thus accomplish 
an accompanying movement of oil from the 
place of origin to the reservoir. 
I regret that I have not the facilities to 
demonstrate experimentally these principles, 
since they would be easily put to the test, 
given the required apparatus. 
As to their practical bearings, 
(a) Since the shale can contribute to a 
neighboring sandstone reservoir, contiguous 
bodies of organic shale and limestones would 
be considered favorable circumstances, rather 
than negligible as held by I. C. White, who 
finds the origin of the oil and gas within the 
sandstone. 
(b) A reservoir may be expected to receive 
its oil and gas from shale above as well as 
below. 
(c) A sandstone embedded within shales 
that seem to have very little oil in them may 
