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Updated: May 3, 2025
At the cataracts of the great rivers Orinoco, Nile, and Congo, the syenitic rocks are coated by a black substance, appearing as if they had been polished with plumbago. The layer is of extreme thinness; and on analysis by Berzelius it was found to consist of the oxides of manganese and iron.
To explain more clearly, it was the practice of most silver platers to use an alloy for silver-plating. In the reduction of the ingot to sheet metal, annealing has to be resorted to, and acid pickles to remove oxides, etc. The number of times the plated metal is exposed to heat and acid in its reduction to the required thickness, produces a surface of pure silver.
Adopting this hypothesis, it may be asked whether the river holds the oxides suspended like sand and other earthy substances, or whether they are found in a state of chemical solution. The first supposition is less admissible, on account of the homogeneity of the crusts, which contain neither grains of sand, nor spangles of mica, mixed with the oxides.
Over the gates the large oval space is filled with the sacred monogram I.H.C. The base consists of polished Devonshire marble. The diversity of tint of the metals used is in itself a source of colour, but the whole of the hammered iron-work of the foliage has been painted with oxides of iron and copper, while the colour scheme is further carried out in the mosaics.
The metal which had been destroyed is revivified by the grains of wheat and the action of fire. Is this not to perform the miracle of the resurrection? No objection can he raised to this interpretation, as long as we are ignorant of the phenomena of oxidation, and the reduction of oxides by means of carbon, or organic substances rich in carbon, such as sugar, flour, seeds, etc.
The great mass of the earth was shown to be composed of metals in combination with oxygen, to which they are united in one, two, or more definite and unalterable proportions, forming compounds which are termed metallic oxides, and these, again, combined with oxides of other bodies, essentially different to metals, namely, carbon and silicium.
Painted patterns are not uncommon upon the glazed pottery, though upon the unglazed they are scarcely ever found. The most usual colors are blue, yellow, and white; brown, purple, and lilac have been met with occasionally. These colors are thought to be derived chiefly from metallic oxides, over which was laid as a glazing a vitreous silicated substance.
In its presence the insoluble iron oxides which give color to most red and yellow rocks are decomposed, leaving the rocks of a gray or bluish color, and the soluble iron compounds which result are readily leached out, effects seen where red or yellow clays have been bleached about some decaying tree root.
A good strong heat may therefore at once be applied to the retort and continued, the effect being to oxidise the arsenic, antimony, lead, etc., which, in the form of oxides, will not again amalgamate with the mercury, but will either lie on its surface under the water, into which the nozzle of the retort is inserted, or will float away on the surface of the water.
To me this planet is a little ball of oxides and nickel steel; life a sort of tarnish on its surface. And we, the minutest particles in that tarnish. Who can nevertheless, in some unaccountable way, take in the idea of this universe as one whole, who begin to dream of taking control of it." "That is not a bad statement of the scientific point of view.
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