SCIENCE OF COMMON THINGS. 53 



Effect of drainage upon springs. Pressure of water. 



will rise in it, and flow over in a jet proportional to the height of the 

 water accumulated in the stratum from whence it flows. 



305 What general effect does the cultivation and drainage of a country 

 have upon the springs ? 



In a well cultivated and improved country the 

 springs are comparatively few in number and not con- 

 stant, While the face of a country is rough, the rain- 

 water remains long among its inequalities, slowly sink- 

 ing into the earth ,to feed the springs, or slowly run- 

 ning away from bogs and marshes towards the rivers ; 

 but in a well drained, country the water runs off quick- 

 ly, often producing dangerous floods. 



SOS How is the pressure of water exerted? 



Equally in all directions. 



SOT* Does ivater, contained in a vessel, press with as great force against 

 t)ie sides and top as against the bottom ? 



The pressure, in all directions, is the same 



SOS What is the result if a corked empty bottle be lowered into the 

 ocean for a considerable depth ? 



The cork is generally forced inwards at a given 

 depth, no matter in what direction the mouth of the 

 bottle may happen to point. 



SOD Jf the cork is fastened immovably into the bottle, what will be the 

 effect? 



The bottle will be crushed inwards by the pressure 

 before it reaches a depth of sixty feet. 



S1O When a ship founders in shallow water, the wreck, on breaking to 

 pieces, generally comes to the surface and is cast upon the shore ; but when 

 a ship sinks in very deep water, it never rises : why is this f 



The pressure of very deep water forces the water 

 into the pores of the wood, and makes it so heavy that 

 no part of the wreck is enabled to rise again. 



311 Can you sink a cork so deep that it will riot rise to the surfact 

 ugain t 



At a great depth the water forced by pressure into 

 the pores of the cork renders it so heavy that it cannot 

 rise. 



313 What is the pressure of water expressed in numbers f 



The pressure of water at any depth, whether on the 

 3* 



