138 PHENOMENA OF THE UNIVERSE. 



is natural results from their conjunction, the bodies of water 

 or air leap back and return, in order to open and loose 

 themselves. 



HISTORY. 



The face of water and of every fluid is uneven after 

 agitation and perturbation, and that by an inequality move- 

 able and successive, till the water regains its proper con 

 sistency and is freed from the pressure : as in the waves of 

 the sea and of rivers, even after the winds have calmed, 

 and in all disturbed water. 



The same kind of inequality is evidently in the winds 

 also, which roll themselves together in the same manner as 

 the waves : neither do they return to tranquillity imme 

 diately on the cessation of the first impetus, except that in 

 the undulation of the air, the motion of gravity, which in 

 water is joined with the motion of liberation from pressure, 

 does not intervene. 



A stone thrown sidelong on the water (as boys do in 

 play) leaps off and repeatedly falls and is struck again by 

 the water. Swimmers when from an eminence they leap 

 headlong into the water, guard against dividing it through 

 the joining of their thighs. Lastly; water struck by the 

 hand or by the body with power, beats like a ferula or any 

 rather hard body, and causes pain. And in skiffs and keels 

 of vessels which are guided by the force of oars, the water 

 pushed forward and borne down by the oars behind the 

 rowers forces the skiff forward, and makes it move on its 

 way, and bound onward as a boat is moved off from the 

 shore by the waterman s pole. For the water, gathering itself 

 behind the stern of the vessel and urging it into a contrary 

 direction, is not the principal cause of this, which never 

 theless arises from the pressure relaxing itself. 



Air, in avoiding compression, imitates and puts forth all 

 the actions of a solid body; as we may see in the winds, 

 which direct the courses of ships, overthrow houses and 

 trees, and prostrate them to the ground. 



The stroke that is given from a sling, hollow and long, 

 so as to help the compression of the air, is owing to the 

 same cause. 



Boys in imitation of cannon scoop out the wood of the 

 alder tree and stop up each end of a squirt with bits of the 

 root of the fleur de luce, or of paper rolled up, and then 

 shoot off the little ball by means of a wooden pin, but before 

 that touches it, the further ball is sent off with an audible 

 force by the power of the air shut up in the squirt. 



