“Perhaps not a day passes without the solid crust of the earth experiencing some shock, sometimes at one point, sometimes at another, beneath the bed of the seas, as well as under the continents. However, disastrous earthquakes are very rare, thanks to the intervention of volcanoes. “Volcanic orifices are, in fact, veritable safety-valves, which put the interior of the globe in communication with the exterior. By offering permanent vents to the subterranean vapors that tend to liberate themselves by overturning the earth, they render earthquakes less frequent and less disastrous. In volcanic countries every time the ground is shaken by strong shocks, the earthquake ceases the moment the volcano begins to throw up its fumes and lava.” “I well remember,” said Jules, “your account of the eruption of Etna and the Catanian disaster. At first I only saw in volcanoes terrible mountains spreading devastation around them; now I begin to see their great use, their necessity. Without their air-holes, the earth would seldom be still.” ------------------------------------------------------------------------ CHAPTER LXX SHELLS IN Uncle Paul’s room was a drawer full of shells of all sorts. One of his friends had collected them in his travels. Pleasant hours could be passed in looking at them. Their beautiful colors, their pleasing but sometimes odd shapes, diverted the eye. Some were twisted like a spiral stair-case, others widened out in large horns, still others opened and closed like a snuff-box. Some were ornamented with radiating ribs, knotty creases, or plates laid one on another like the slates of a roof; some bristled with points, spines, or jagged scales. Here were some smooth as eggs, sometimes white, sometimes spotted with red; others, near the rose-tinted opening, had long points resembling wide-stretched fingers. They came from all parts of the world. This came from the land of the negroes, that from the Red Sea, others from China, India, Japan. Truly, many pleasant hours could be passed in examining them one by one, especially if Uncle Paul were to tell you about them. One day Uncle Paul gave his nephews this pleasure: he spread before them the riches of his drawer. Jules and Claire looked at them with amazement; Emile was never tired of putting the large shells to his ear and listening to the continual _hoo-hoo-hoo_ that escapes from their depths and seems to repeat the murmur of the sea. [Illustration: Cassis] “This one with the red and lace-like opening comes from India. It is called a helmet. Some are so large that two of them would be as much as Emile could carry. In some islands they are so abundant that they are used instead of stones and are burnt in kilns to make lime.” “I would not burn them for lime,” said Jules, “if I found such beautiful shells. See how red the opening is, how beautifully the edges are pleated.”