22 SCIENCE PRIMERS. [MATERIAL 



water, for it runs away between your fingers, and you 

 cannot raise it into a permanent heap. All this shows 

 that the parts of water move upon one another with 

 great ease. The same fact is illustrated if the tumbler 

 is inclined, so that the level of the surface rises above 

 the edge of the tumbler on one side, and the water is 

 therefore to some extent unsupported by the tumbler 

 at this point. The water then flows over in a stream 

 and falls to the ground, where it spreads out and runs 

 to the lowest accessible place, or gradually soaks up 

 into crevices. 



Nevertheless, although the parts of the water thus 

 loosely slip and slide upon one another, yet they hold 

 together to a certain extent. If the surface of the 

 water is just touched with the finger, a little of it will 

 adhere ; and if the finger is then slowly and carefully 

 raised, the adjacent water will be raised up into a 

 slender column which acquires a noticeable length 

 before it breaks. So, in the early morning, after heavy 

 dew, you may see the water upon cabbage-leaves and 

 blades of grass in spherical drops, the parts of which 

 similarly hold together. 



Material substances, the parts of which are so 

 movable that they fit themselves exactly to the sides 

 of any vessel which contains them, and which flow 

 when they are not supported, are called fluids ; and 

 fluids the parts of which do not fly off from one 

 another, but hold together as those of water do, are 

 called liquids. 



Water therefore is a liquid. 



16. Water is almost incompressible. 



It has been seen that water, like every other 



