SCIENTIFIC SUMMAKY. 
389 
while the pick is held loose by a man, or is attached to the piston so as to 
loosen the coal at the dop, bottom, or sides, by elevating or lowering the 
frame on which it stands. A circular saw is also attached to the machine. 
Rocks yielding Petroleum. — In a paper upon this subject, which was pub- 
lished in the Scientific American, the following conclusions relative to the 
proper method of working the petroleum rocks are stated : — - 
(1.) Each widely-separated locality must be governed by its own laws, as 
developed by boring and observation. 
(2.) Each geological horizon of oil-bearing rock, receives its supply not 
from another, but from causes operating at the time of its deposition (!). 
(3.) There is not now any reproduction of oil, but Ave are drawing from 
fountains filled “ of old.” 
(4.) ISio strata are so thoroughly saturated with oil as to form a subterranean 
sheet of rocks where petroleum is sure to be found. The oil occurs in fre- 
quent isolated fissures, at various depths, and of various sizes, and containing 
different grades of oil. 
A thin Plate of Iron. — A curious specimen of rolled iron was some time 
ago transmitted to the Birmingham Journal. It consisted of an extremely 
thin sheet of the metal, which had been used instead of paper as a medium 
of correspondence. The writer, dating from South Pittsburg, says, “ In the 
number of your paper dated October 1st there is an article setting forth that 
John Brown & Co., of Sheffield, had succeeded in rolling a plate of iron 13^ 
inches thick. I believe that to be the thickest plate ever rolled. I send you 
this specimen, prepared at the Sligo Works, Pittsburg, as the thinnest iron 
ever rolled in the world up to this time.” 
The iron sent appears to be of exceedingly fine quality, and the sheet is by 
far the thinnest ever seen in this country. Tested by one of Holtzapffel’s 
gauges, the thickness of the sheet was found to be the one thousandth of an 
inch I A sheet of Belgian iron, supposed hitherto to be the thinnest yet 
rolled, is the six hundred and sixty-sixth part of an inch thick ; and the 
thickness of an ordinary sheet of note-paper is about the 400th of an inch. — 
Vide The Artizan, January. 
The Conversion of Iron into Steel. — The many complex questions relating 
to this process having lately engaged the attention of many members of the 
French Academy, M. Caron was induced to make a series of experiments, 
the results of which he has reported. A bar of iron one centimetre square, 
and thirty centimetres long, was heated in a long earthen tube filled with 
graphite, broken into pieces about a cubic centimetre in size. The extremi- 
ties, which had been imperfectly plugged with two pieces of graphite, allowed 
the air to enter the tube, while the latter, itself being porous, was traversed by 
the gases of the furnace. The entire apparatus was exposed to a cherry-red 
heat fotf six hours, at the end of which time the bar was drawn from the 
tube and hammered and tempered preparatory to its examination. The 
metal was fibrous ; it could hardly be bent when cold, Avithout being com- 
pletely shattered ; its surface was easily acted on by the file ; in fact it gaAT 
no trace of having become steel. Other experiments gave like results. 
From these M. Caron concludes that graphite is not the only carbon inca- 
pable of converting iron into steel. Lamp-black, probably coke, and aU 
carbons deprived of alkalies and carburetted gases, Avill give the same results. 
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