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Besides these, a small Onichidium, and a new kind of shelled snail. In the mossy woods live a large, yellowish, black-spotted Limax, and two Helices of middling size. In the bay itself are found a few of the gilled snails with spiral shells; and a considerable number on the outward coast, which is washed by the ocean.
The fresh-water basins were filled with Helices, one of which is represented in the following wood-cut, with Planorbis, Limnæus and other Shells resembling those now so common in all our lakes and rivers, and differing from the living ones only by slight specific characters.
Why are these little pebbles preferred to chips of lime-stone, when both materials are found in equal abundance around the nest? A yet more remarkable feature: we find pretty often, encrusted on the dome, a few tiny, empty snail-shells, bleached by the sun. The species usually selected by the Eumenes is one of the smaller Helices Helix strigata frequent on our parched slopes.
The two colleagues shrugged their shoulders. That was probably what the engineer was waiting for. Robur made a sign. The propelling screws immediately stopped, and after running for a mile the "Albatross" pulled up motionless. At a second gesture from Robur the suspensory helices revolved at a speed that can only be compared to that of a siren in acoustical experiments.
The land molluscs of the district are the only animals which aestivate; they are found in clusters, Bulimi and Helices, concealed in hollow trees, the mouths of their shells closed by a film of mucus. The fine weather breaks up often with great suddenness about the beginning of February. Violent squalls from the west or the opposite direction to the trade-wind then occur.
'On the outside of the helices, to quote the description, 'was placed a line of pieces of metal, so arranged as to render the attachment with the battery and its necessary alternations performable by the engine itself.
Thus J.J. Thomson shows that if, in certain conditions, a conductor is placed in a magnetic field, the ions have to describe an epicycloid, and their journey is thus lengthened, while the electric resistance must increase. If the field is in the direction of the displacement, they describe helices round the lines of force and the resistance is again augmented, but in different proportions.
Before we close, we must mention some very recent experiments that have been made with a torpedo analogous to Whitehead's, that is to say, one that runs alone by means of helices actuated by compressed air, but having the great advantage that it can be steered at a distance from the very place whence it has been launched.
A differential galvanometer was connected with the other helices in such a manner that when a voltaic current was sent through the middle helix its inductive action on the lateral helices should cause currents in them, having contrary directions in the coils of the galvanometer.
As she spun the "Albatross" was carried along by the spout, which pirouetted along the waves with a speed enough to make the helices jealous. And if she escaped from the spout she might be caught by another, and jerked to pieces with the shock. "Get the gun ready!" said Robur.
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