The points of the piles, whatever be their form and arrangement, are strengthened by means of steel pieces, which assure of their penetrating hard and compact earth.

[Illustration:  Fig. 3.—­Dredging within A space circumscribed by iron pile planks.]

Fig. 2 represents a dredge at work within a space entirely circumscribed by pile planks.  Here, after the excavation is finished, beton will be put down by means of boxes with hinged bottoms, and the water will afterward be pumped out in order to allow the masonry to be constructed in the open air.  Fig. 3 shows a transverse section of two of these pile planks united by mortar joints.  This system is the invention of Mr. Papenot.—­Revue Industrielle.

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AN ATMOSPHERIC BATTERY.

Great ingenuity is being shown in the arrangement of new forms of primary batteries.  The latest is that devised by M. Jablochkoff, which acts by the effect of atmospheric moisture upon the metal sodium.  A small rod of this metal is flattened into a plate, connected at one end to a copper wire.  There is another plate of carbon, not precisely the same as that used for arc lights or ordinary batteries, but somewhat lighter in texture.  This plate is perforated, and provided with small wooden pegs.  The sodium plate is wrapped in silk paper, and pressed upon the carbon in such a manner that the wooden pegs penetrate the soft sodium.  For greater security the whole is tied together with a few turns of fine iron wire; care being taken that the wire does not form an electric contact between the sodium and the carbon.  The element is then complete, the carbon and the small copper wire being the electrodes.  The sodium, on exposure to the air, becomes oxidized, forming caustic soda, which with the moisture of the air dissolves, and drains gradually away in the form of a concentrated solution; thus constantly exposing the fresh surface of the metal, which renders the reaction continuous.  The price of the element is lower than would be expected at first sight from the employment of so expensive a metal.  The present cost of sodium is 10 frs. per kilogramme; but M. Jablochkoff thinks that on the large scale the metal might be obtained at a very low figure.  The elements are grouped in sets of ten, hung upon rods in such a manner that the solution as formed may drain off.  Such a battery continues in action as long as the air contains moisture; the only means of stopping it is to shut it up in an air-tight case.  The electro-motive force depends on the degree of humidity in the air, and also upon the temperature.

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Analysis of perfumed scouring pastes.—­The analysis of No. 1 resulted in water and traces of myrbane oil, 3.66 per cent.; fatty acid, melting at 104 deg.  F., 54.18 per cent.; iron peroxide, 10.11 per cent.; silicic acid, 14.48 per cent.; alumina, 17.31 per cent.; lime and magnesia, traces.  The iron peroxide is partly soluble in hydrochloric acid, the alumina entirely so as silicate.  The scouring paste, therefore, is composed of 54 per cent. fatty (palm oil) acid, 10 per cent. jeweler’s rouge, 32 per cent. pumice-stone powder.