76 PHYSIOLOGY OF THE CIRCULATION. 



extremity, it instantly rose in the vertical glass tube 

 to a height of nine inches, and continued at that 

 elevation as long as the same column of water was 

 maintained in the reservoir. On allowing the latter 

 to fall to ten inches, the same proportion was still 

 observed between its height and that of the fluid in 

 the glass tube, which had, during the same time, 

 fallen to seven and a half inches. 



Exp. 3. Every other condition being precisely 

 similar, the tube one-third of an inch wide was with- 

 drawn from the outer orifice of the tin pipe, and re- 

 placed by one one-sixth of an inch in diameter. On 

 the re-admission of water into the tin pipe, it instantly 

 rose in the glass tube to within half an inch of the 

 height of the column in the reservoir, viz. to eleven 

 and a half inches, though a jet one-sixth of an inch 

 in diameter was, at the same time, escaping through 

 the outer orifice of the horizontal pipe. A finger 

 was now placed upon the inner orifice of this pipe, 

 where it projected into the reservoir, and slowly 

 drawn over it, so as gradually to diminish the area 

 of the stream of water entering it ; and it was ob- 

 served that, in proportion as that diminution took 

 place, there was a corresponding fall of the fluid in 

 the glass tube, till, with a certain extent of closure 

 of the inner orifice, there ceased to be any ascent of 

 water in the vertical tube. 



When the column in the reservoir was allowed to 

 fall, the same proportion between its height and that 

 of the water in the glass tube was still preserved, the 

 difference never exceeding half an inch. 



In these experiments it was very evident that the 



