Hence the blast furnace process, thus freed from the hampering need of controlling accurately the silicon-content, can be much more effectively guided so as to prevent the sulphur from entering the pig iron.
The reason for this is that in it the slag, by means of which all the purification must needs be done, is not heated effectively; that hence it is not readily made thoroughly liquid; that hence the removal of the phosphoric slag made in the early dephosphorizing stage of the process is liable to be incomplete; and that hence, finally, the phosphorus of any of this slag which is left in the furnace becomes deoxidized during the second or deoxidizing stage, and is thereby returned to befoul the underlying steel.
The reason why the slag is not heated effectively is that the heat is developed only in the layer of metal itself, by its resistance to the induced current, and hence the only heat which the slag receives is that supplied to its lower surface by the metal, while its upper side is constantly radiating heat away towards the relatively cool roof above.
Bright orange, yellow, red and purple hues predominate and are set off very effectively against the dark green pines with which the margins of the canyon are fringed, and the white foam of the river at the bottom of the chasm.
In the established Church of England the appointment of bishops is vested effectively in the crown, though the old form of election by the cathedral chapter is retained.