380 
Petroleum : its Sources and Uses. 
does not appear to belong to any particular geological formation, 
inasmuch as it occurs in Europe usually in rocks of the Tertiary 
period, while in the United States it is found in the Devonian and 
Silurian strata, which are so nearly devoid of animal and vegetable 
remains. He also points out that, on account of the volatile nature 
of rock oil, it could not have been borne from a distance like many 
other deposits, but must have been formed very near the spot wliere 
it is found. The fissuring of the earth’s crust by the upheaval of 
mountain chains and by other disturbances allows surface-waters to 
penetrate into the heated intei'nal portions of the earth ; and there, 
coming in contact with the glowing metals and their carbides, they 
give rise to the chemical reactions which result in the formation of 
petroleum in the state of vapour, and in the evolution of steam. 
These vapours penetrate through the fissured crust into the upper 
and cooler regions, where they are either wholly or partially con- 
densed, forming deposits of petroleum very commonly associated 
with water ; and the gases which cannot be condensed by cold 
escape to the surface. The precise compounds which are formed 
depend upon the temperature and pressure met with j and hence we 
find associated every grade of product — gas, oil, mineral pitch, 
ozokerit, and other substances. Tlie extraordinary average persist- 
ence of the oil wells leads to the conviction that the substance must 
be forming as fast almost as it is removed ; and I have very little 
doubt that improved boring appliances will enable engineers to 
penetrate to depths not even dreamt of now. Hence, it is likely 
that, by the time that our coal resources come to an end, from the ex- 
haustion of the mineral, or from the condition of perpetual strike 
to which we seem tending, oil springs will be tapped which will 
have the priceless advantage of yielding their riches without the 
agency of underground labour.* 
W. Axdersox. 
THE CURE OF SHEEP SCAB, 
The Editor of the Journal lias received tlie following cohimuhicd- 
tion, dated April 28 last, from Messrs. Wm. Cooper & Nephews, 
and in reference to the subjoined resolution passed by the Council 
“ Messrs. William Cooper and Nephews and other manufacturers of pro- 
prietary Sheep Dips having called the attention of the Council to a paper 
which appeared in the March number of the Journal by Mr. P. R. Gordon, 
Chief Inspector of Stock in Queensland, animadverting on those Dips, the 
Council wish at the earliest moment to announce publicly that they do not 
themselves accept the whole of the views expressed by Mr. Gordon with 
‘ A more extended account of Dr. Mendelecff’s theory will be found in the 
lieport of the British Association for 1889 (Newcastle-upon-Tyne Meeting) in 
Dr. Anderson’s Presidential Address to Section G (Mechanical Science), pages 
727-730. 
