Petroleum and other Owls as a Fuel. 285 
agent there are, in large mines generally three or four at 
least ; of whom, those. whose attention is confined to the 
workings in the mine, are called “ underground captains,” 
and those to whom devolve the highest duties of experi- 
mental research upon the surface, are termed “grass cap- 
tains.” 
The sinking of a shaft is effected by making an aperture 
in the ground about six feet across, and as near square as 
may be, which the miner continues to sink, in the daily and 
hourly expectation of arriving at the vein whose supposed 
existence had tempted the excavation. If he should be 
fortunate enough to find it a reasonable and proper depth, 
it then remains to be considered in what manner it ought 
to be treated ; in other words, whether its appearances are 
sufficiently promising to justify further toil and expense, 
and if they do, whether it ought to be worked to the east 
or to the west, &c. 
If, on the other hand, he should not succeed in striking 
upon the point he had been in quest of (after arriving at a 
depth at which it is reasonable to suppose the ore ought to 
be met with), it then remains to be considered, whether the 
shaft has not been sunk too much to the north or too much 
to the south, so as to have missed the vein; and in ‘such 
case, a cross-cut is generally ordered in each of those direc- 
_ tions, to a distance beyond which the vein could not be 
supposed to lie; and, if inso doing, no indication of copper 
should be found, the earth is pronounced to have been 
proved, and it is concluded that the lode does not run in 
that direction. 
(To be continued.) 
Ste VALUE OF PETROLEUM AND OTHER 
OIES io ce POE, 
a a recent number, we adverted to the experiments on 
burning petroleum, carried on in America, the follow- 
ing, on the official report of experiments at Woolwich, ap- 
peared in the Standard :— 
The engineers of the Woolwich Dockyard have returned 
to the Admiralty, we hear, a statement, without comment, 
of what Mr. Richardson has done, and have accompanied 
their statement with a drawing of the apparatus by which 
