128 



FERGUSON'S LECTURES. 



Intermit- 

 ting 

 spring*. 



LECT. an d be discharged at F. But as the bore of the syphon 

 ,x-\ -x*/ is larger than the bore of the pipe, the syphon will run 

 faster than the pipe, and will soon empty the vessel B; 

 upon which the water will cease from running through 

 the syphon at F, until the pipe C re-fills the vessel B, 

 and then it will begin to run as before. And thus the 

 syphon will continue to run and stop alternately, until 

 all the water in the vessel A has run through the pipe 

 C. So that, after a few trials, one may easily guess 

 about what time the syphon will stop, and when it will 

 begin to run : and then, to amuse others, he may call 

 out stop, or run, accordingly. 



Upon this principle, we may easily account for inter- 

 mitting or reciprocating springs. Let A A be part of a 

 hill, within which there 

 is a cavity B B ; and 

 from this cavity a vein 

 or channel running in 

 the direction B C D JE. 

 The rain that falls 

 upon the side of the 

 hill will sink and strain 

 through the small pores 

 and crannies G, G, G, 

 G; and fill the cavity with water K. When the water 

 rises to the level H H C, the vein B CD E will be 

 filled to C, and the water will run through C D F as 

 through a syphon ; which running will continue until 

 the cavity be emptied, an /J then it will stop until the 

 cavity be filled again. 



The com- The common pump (improperly called the sucking 

 > r - ? vn 'P- pump), with which we draw water out of wells, is an 

 engine both pneumatic and hydraulic. It consists of a 

 pipe open at both ends, in which is a moveable piston 

 or bucket, as big as the bore of the pipe in that part 

 wherein it works ; and is leathered round so as to fit the 

 bore exactly; and maybe moved up and down, without 



