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LECTURES TO SCIENCE TEACHERS. 



another, but are smaller than those at E and P. The area 

 at I is the smallest of all. Now, the fluid being friction- 

 less, the pressures at E and P indicated by the heights E D 

 and P Q would be equal, these being greater than C H and 

 K N. C H and K N would also be equal to one another, 

 and would be themselves greater than I J. 



FIG. 9. 



The results shown in Fig. 9 are similar in kind, equal 

 pressures corresponding to equal sectional areas. 



But if the experiment were tried with water, some of the 

 pressure at each successive point would be lost in friction, 



FIG. 



and this growing defect in pressure, or " gradient," would 

 be indicated in the successive gauge-glasses in the manner 

 shown in Figs. 10 and 11. 



I have here arranged an experiment which conveniently 



