List of Recent Publications. 205 
containing it : the geological structure of the region and its effect on the 
distribution of the gas fields; the duration of the gas and the means for 
measuring and protecting its use are all treated of in a thoroughly- 
scientific and comprehensive manner. Seldom does an annual rjport 
contain such an able and entertaining as well as conclusive and con- 
vincing treatment of any subject, especially one so new and little studied 
as this. Dr. Orton's style is easy, and his meaning is never obscure. 
Not the least valuable and instructive part of the report is the review 
of the various theories hitherto proposed for the origin of petroleum and 
natural gas. These are divided into two classes, Chemical and Geolog- 
ical. Under the head of Chemical theories are mentioned that of Ber- 
thelot ( 1866 ) which accounted for all natural hydrocarbons by the action 
of chemical forces on inorganic matter at considerable depth within the 
earth's crust ; and that of Mendeljeff (1877) which "holds that petro- 
leum is never of organic origin, but is as purely a product of chemical 
affinity, acting on inorganic substances, as a vein-stone or an ore." 
Both of these chemical theories are found to be inadequate to explain 
the origin of petroleum. 
Under the head of Geological Theories are mentioned those of New- 
berry, Peckham, Hunt and others, and we find that they all agree in 
deriving petroleum from organic substances that were incorporated with 
the strata when the latter were formed. Most geologists hold that 
vegetable substances have supplied the chief sources, but some count 
animal remains as also an important source. The two methods in which 
organic matter may have furnished petroleum are ( 1 ) by destructive 
distillation and ( 2 ) by primary decomposition. According to the latter 
view, which is the one held by Hunt, the petroleum that the rocks 
contain was formed when the rocks themselves were formed, and this 
process of formation therefore e*eased long ago in the older rocks. Al- 
though Dr. Orton does not adopt fully any of these theories, he looks 
upon the last one mentioned "with great interest as it furnishes on the 
whole the best explanation of the facts for which we are obliged to 
account." 
A detailed history of each of the great Ohio gas wells up to date is 
given and many popular opinions, such as the belief in the eternal 
duration of the gas supply, the existence of vast subterranean caverns 
which may open and engulf whole cities, and others equally well- 
founded are exploded. 
LIST OF RECENT PUBLICATIONS. 
3. Papers in Scientific Journals. 
American Journal of Science ami Arts, <)<■!. No. Description of the 
"Bernardston scries" of metamorphlc upper Devonian rocks, B. K. 
Emerson: Metaeinnabarite from New Almaden, Cal., W. II. Melville; 
Keokuk beds at Keokuk, Iowa, C. II. Gordon : Experiments on the con- 
