444 APPENDIX. 



Letting t represent the number of seconds required to make one 

 revolution, 





 v 



Remembering that TT = 3.14159, we have 



Representing the number of revolutions per second by n, we have 

 v = 2 irm. /. C. F. = 1.2275 wrn*. 



Caution. In using these last two formulas for "centrifugal 

 force," care must be taken that radius be expressed in feet. 



APPENDIX D. 



Prince Rupert Drops. A neat illustration of the trans- 

 mission of pressure by liquids ( 216), may be given by filling a 

 small bottle with water, holding a Prince Rupert drop in its mouth, 

 and breaking off the tapering end. The whole " drop " will be in- 

 stantly shattered and the force of the concussion transmitted in 

 every direction to the bottle which will be thus broken. These 

 "drops" are not expensive ; they may be obtained from James W, 

 Queen & Co., 924 Chestnut street, Philadelphia. 



APPENDIX E. 



Difference between Theory and Practice. The re- 

 sults mentioned in 256 are never fully attained in practice. Only 

 the particles near the centre of the jet attain the theoretical velocity. 

 Further than this, if we carefully examine the stream we shall 

 notice that at a little distance from the orifice the stream is not more 

 than two-thirds or three-fourths the size of the orifice. This is due 

 to the fact that the liquid particles come from all sides of the 

 opening, and thus flow in different directions, forming cross currents, 

 which may be seen if there are solid particles floating in the water. 

 These cross currents impede the free flow and diminish the volume 

 of liquid discharged. Short cylindrical or funnel-shaped tubes in- 

 crease the actual flow. In a cylindrical tube, this narrowing of the 

 jet could not take place without forming a vacuum around the nar- 

 row neck (called the vena contracta}. The pressure of the atmos- 

 phere, tending to prevent this formation of such a vacuum, increases 



