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To apply Schmidt's law it is necessary to know accurately what is the strike and underlay of both the lode and cross-course ; this can best be determined by actual survey in the mine where two levels have been opened ; but where this is not the case the average strike of the reef and cross-course can only be taken in the level being driven, the underlay being determined by the plumb bob or clinometer.

Having once got back to older rocks, which evidently have themselves contained the mineral deposits from which the alluvial was derived, many other points have to be considered in addition to those already dealt with. The fact that the stream has been engaged in gorge-cutting and lowering its bed is likely to have led to frequent changes in its course, and any indications of such changes must be jealously looked for. Such a change would be likely to have left a stretch of the old river bed stranded on one or other side of the existing stream.

Fluor Spar is a lode-forming mineral, sometimes alone, but also associated with other minerals, especially tin ore and galena. In the lead mines of Derbyshire and Cumberland, which are in limestone, it is found in beautiful crystals of conspicuous colours, and, when obtained in blocks of sufficient size, is worked into vases and other ornaments.

Bearing in mind the numerous movements of elevation or depression to which strata have been subjected since they were originally formed, and the dislocation to which these movements have given rise, it becomes possible to investigate the origin and characters of metalliferous deposit occurring in lodes or fissures in the rocks.

 Welding GMAW (Gas Metal Arc Welding) is a semi-automatic or robotic welding that uses a continuous consumable electrode and is fed into the gun along with the inert gas MIG or MAG welding gas active in creating the atmosphere protective. Does not need to constantly be changing electrode.

Plasma Welding: In the welding electrical current through two electrodes with tip, due to the strength of the material to be bonded to achieve the heating and applying pressure on parts generates a spot weld. The point welding machines can be fixed or mobile or be attached to a robot or mechanical arm.
The electron beam welding is a welding process in which the energy required to melt the material is supplied by an electron beam.

 Plasma arc welding is technically known as PAW (Plasma Arc Welding), and uses the same principles as TIG welding, as can be seen as a development of this latter process. However, both the energy density as the temperatures are much higher this process since the plasma state is reached when a gas is heated to a temperature sufficient to achieve its ionization, thus separating the element into ions and electrons.

Stratified beds of ironstone occur under somewhat similar conditions to coal, but they are much less regular in extent. They are frequently found associated with coal measures, but are quite as often interstratified with beds in which no coal is present. Most stratified deposits of iron are carbonate of iron, mixed either with clay as clay band ironstone, or clay and carbonaceous matter as black band ironstone.

The occurrence of alluvial gold or tinstone leads the prospector to examine the country for the reefs from which these have been shed, and a careful study of the conditions which prevail will afford much information. In the case of surface deposits, it is evident that the country in the immediate vicinity should be examined ; but where the alluvial deposit has been found in the beds of existing streams or old river channels, it is equally obvious that it may have travelled a long distance from its parent reef.

HAVING alluded to all the different conditions under which minerals occur, either as reefs or stratified deposits, it is now proposed to devote a chapter to a description of those repositories of minerals known as alluvial deposits. All alluvial deposits have been formed by the degradation of the lodes or other ore bodies already described, with their accompanying rocks, or of rocks impregnated with mineral.