SCIENTIFIC SUMMARY. 
211 
crystals of the coarser kinds, as compared with those of the finest qualities 
of crystalline ironware of about twice the height. The more uniform the 
grain, the smaller the crystals, and the flatter the pyramids which form 
each single element, the better is the quality, the greater is the cohesive 
force, and the finer the surface of the iron. These pyramids become flatter 
as the proportion of carbon contained in the steel decreases. Consequently 
in cast iron and in the crudest kinds of hard steel the crystals approach 
more the cubical form, from which the octahedron proper is derived, and 
the opposite extreme or wrought iron has its pyramids flattened down to 
parallel surfaces or leaves, which in their arrangement produce what is called 
the fibre of the iron. The highest quality of steel has all its crystals in 
parallel positions, each crystal filling the interstices formed by the angular 
sides of its neighbours. The crystals stand with their axes in the direction 
of the pressure or percussive force exerted upon them in working. 
The Commercial Preparation of White Lead. — We learn from the Chemical 
News that an invention is at present being tested by which ordinary galena, 
after having been crushed in an ore crusher, is roasted in a desulphurising 
kiln, and next mixed with carbon (preferably in the state of fine-washed 
pea or dust anthracite coal) in the proportion of half and half. This mix- 
ture is heated in a peculiarly constructed furnace ; and the dense white 
vapours which are given off are conveyed into a separate chamber, and 
strained by passing through bags or screens of muslin, or are allowed to 
deposit slowly, and, after cooling, collected, as in the case of the manufacture 
of zinc-white. 
Gold in the Laurentian Rocks of Nova Scotia. — Professor Hind has lately 
made a report on the rocks which, according to him, represent the Lauren- 
tian system of Sir W. Logan. The Mining Journal states that Professor Hind 
considers these rocks to consist of sedimentary deposits, altered by meta- 
m orphic action, and that their crystalline structure was produced before the 
deposition of the gold-bearing rocks which lie unconformably upon them. 
Gold is found and worked in the Laurentian rocks in Canada, as at the 
Madoc Mines, and it is not improbable that mines may yet be opened in the 
Laurentian of Nova Scotia. The area occupied by the Laurentian in Nova 
Scotia is probably not less than one-half that part of the country which 
has hitherto been represented on geological maps as Lower Silurian. 
The Laurentian, being auriferous inferential ly, may yet turn out to be as 
valuable in mineral wealth as the Silurian deposits now worked. In Canada, 
there are, besides gold, beds of magnetic iron ore, of sulphurets of iron and 
copper, and of titaniferous iron ore in these rocks, which may also be found 
in the Laurentian of Nova Scotia, and being in close proximity to the coal- 
fields, may yet prove a great source of wealth. 
A new Explosive for Mines. — A substance which has been called Dualin 
is now coming pretty extensively into use among American miners. It is 
a yellowish-brown powder, resembling in appearance Virginia smoking 
tobacco. It will, if lighted in the open air, burn without exploding ; but, if 
confined, it may be made to explode in the same manner as common powder. 
It is not sensitive to concussion ; will not decompose by itself, nor cake or 
pack together; may be readily filled into cartridges; and it matters not 
whether the place where it is stored be warm or cold, dry or damp. It has 
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