148 WELLS'S NATURAL PHILOSOPHY. 



dij^ped, fills np the little interstices, or spaces, betivecn the fibers, and in this 

 way preveuta all capillary attraction. 



9. Why is vegetation on the margin of a stream of water more luxuriant than in an 

 open field ? 



Because the porous earth on the bank draws up water to the roots of tho 

 plants by capillary attraction. 



10. Why do persons who water plants in pots frequently pour the water into the sau- 

 cer in which the pot rests, and not over the plants"? 



Because tho water iu the saucer is drawn up by capillary attraction through 

 the little interstices of the mold with which the pot is filled, and is thus pre- 

 sented to the roots of the plant. 



IL Why does dry wood, immersed in water, swell ? 



Because the water enters tlie pores of wood by capillary attraction, and 

 forces the particles further apart from each other. 



12. WHiy will water, ink, or oil, coming in contact with the edge of a book, soak fur- 

 ther in than if spilled upon the sides ? 



Because the space between the leaves acts in the same manner as a small 

 capillary tube would — attracts the fluid, and causes it to penetrate far inward. 

 The fluid penetrates with more difficulty upon the side of the leaf, because 

 the pores in the paper are irregular, and not continuous from leaf to leaf 



13. In a hydrostatic press, the area of the base of the piston in the force-pump is one 

 square inch, and the area of the base of the piston in the large cylinder is fourteen square 

 inches ; what will be the force exerted, supposing a power of eight hundred pounds ap- 

 plied to the piston of the force-pump ? 



14. A flood-gate is five feet in breadth, and sixteen feet in depth : what will be tho 

 pressure of water upon it in pounds ? 



15. What pressure will a vi'sscl, having a superficial area of three feet, sustain when 

 lowered into the sea to the depth of five hundred feet ? 



16. What pressure is exerted upon the body of a diver at the depth of sixty feet, sup- 

 posing the superficial area of his body to be two and a half square yards ? 



17. "Wliat will be the pressure upon a dam, the area of tho side of wliich is one hun- 

 drcd and fifty superficial feet, and the height of the side fifteen feet, the water rising even 

 with the top ? 



CHAPTER IX. 



HYDRAULICS. 



_ , , 334, Hydr.\ulics is that department of 



inniat is trie 



science of Hy- phvsical sciciice which treats of the laws and 



draulics ? ^ -^ „,..,. 



phenomena or hquids in motion."-' 



Hydraulics considers the flow of liquids in pipes, through orifices in the 

 sides of reservoirs, in rivers, canals, etc., and the construction and operation 

 of all machines and engines which are concerned in tho motion of liquids. 

 • From iiiojfi (hudor), water, aad uuXiSf (aulos), a pipe. 



