The construction of a transparent globe containing air and liquid, and also of a smaller globe, in the centre, in imitation of the world. Two hemispheres of glass are made (fig. 46): one of them is covered with a plate of bronze, in the middle of which is a round hole, To fit this hole a light ball, of small size, is constructed, and thrown into the water contained in the other hemisphere: the covered hemisphere is next applied to this, and, a certain quantity of liquid having been removed from the water, the intermediate space will contain the ball; thus by the application of the second hemisphere what was proposed is accomplished. 47. _A Fountain which trickles by the Action of the Sun’s Rays._ [Illustration: Diagram of apparatus as described in text] The “fountain” as it is called may be made to trickle as long as the sun falls upon it. Let there be an air-tight pedestal, A B C D (fig. 47), through which a funnel is inserted, its tube extending within a very little of the bottom. Let E F be a globe, from which a tube leads into the pedestal, (reaching nearly to the bottom of the pedestal and to the circumference of the globe,) while a bent siphon, fitted into the globe, leads into the funnel. Now pour water into the globe; and when the sun falls upon the globe, the air in it, being heated, will drive out the liquid, which will be carried along the siphon G, and pass through the funnel into the pedestal. But when the globe is in the shade, the air having escaped through the globe, the tube will again suck up the liquid, and fill the void which had been produced; and this will take place as often as the sun falls upon the globe. 48. _A Thyrsus made to whistle by being submerged in Water._ [Illustration: Diagram of apparatus as described in text] By immersing a thyrsus in water to produce the sound either of a pipe or of any bird. Let A B C D (fig. 48), be a thyrsus; and at the extremity of its head, which must be hollow and shaped like a fir-cone, let there be an orifice D. Close the shaft a little below the mouth by the partition A E, and place near it a small pipe, F, just beneath the mouth of the tube, and passing through an orifice in the partition. If we insert the thyrsus in water and force it downwards, the air contained in it being driven out by the water will produce a sound. If there is nothing but the pipe we shall have a whistle only; but if there is any quantity of water under the partition there will be a gurgling sound. 49. _A Trumpet, in the Hands of an Automaton, sounded by compressed Air._ [Illustration: Diagram of apparatus as described in text]