Bitiiiiii)wiis and Oil Rochs. — Broadhcad. 29 
It is thought b\- some that the oily product of certain rocks 
is of animal origin, and the evidence is, that fossil fish are al- 
most the only fossils f(iund in the Trias of the Connecticut 
valley. Fish remains are common in other oil-producing 
shales, as the black shales of Saarbruck. Prussia. Autun and 
near Clermont, France, and the Zechstein of Mansfeldt. 
Professor Peckham regards all bitumens as having been 
originally derived from either animal or vegetable remains, 
but that the manner of their derivation has not been uniform. 
Oils vary in density from the lightest naphtha, to thick vis- 
cid fluids, and pass by gradation into asphaltum and solid bi- 
tumen. 
John F. Carll of Pennsylvania gave a general vertical sec- 
tion of over 600 feet from the top of the upper barren Coal 
Measures to the Comiferous inclusive, in which he defines 
four distinct oil rocks below the Carboniferous. 
Dr. Ansted considered gas springs the product of the 
same kind of action that produced petroleum ; and on observ- 
ing gas discharges at Pescara, Italy, and in the Crimea, did 
not interpret the phenomena as volcanic, but as associated in- 
cidents of the dying out of the metamorphic action, which i" 
most cases by invading strata containing organic matter, dis- 
tilled all the forms of bitumen, including inflammable gas. In 
the Appalachians, the accumulations of gas are often found 
upon the anticlinals of the pebble conglomerates "and sand- 
stones that hold the petroleum, while at the lower level, in the 
troughs of the synclinals, salt water occurs; but there is no 
evidence of volcanic action. Professor Lesley concluded that 
gas is a direct product of petroleum by spontaneous evapor- 
ation. If so, the life of gas production will be limited by the 
amount of volatile elements held in a definitely limited quan- 
tity of petroleum existing under ground. 
Asphaltum is regarded as the ultimate result of a series of 
changes which take place, under certain conditions, in organ- 
ized matter, producing 1st, naphtha; 2d, petroleum; 3d, min- 
eral tar ; 4th, asphalt or hard bitumen. They merge into each 
other by insensible degrees, so that it is impossible to say 
when mineral tar ends and asphalt begins. Asphaltic stone 
is stone in which the substance will harden and it has become 
verv valuable as a paving material. Gesner says that bitu- 
mens will vield a whole series of hvdrocarbon oils. 
