350 G. H. KNIBBS. 
Table IIT. 
Values of the Index of Roughness (n) and of the index of 
fluidity q. 
ipe. n - q 
Very smooth lead pipes (Reynolds) 1:70 69 “26 
Lead pipes generally (Darcy) 1:78 56 23 
Sheet iron pipes coated with tar _,, 1-79 56 ‘22 
Jointed glass pipe ie i ter FSi ‘BB ‘21 
Drawn iron pipe... as os He E85 ‘54 ‘20 
New cast iron pipe is oe ae 4 “52 17 
Incrusted cast iron pipe... ay ee ie gs ‘51 16 
Table IV. 
l+p 
Values of &, » , and of the index of fluidity,’ etc. 
n 1-70 1°75 1:80 1:85 1:90 1:95 20 
(gp/8n,) » “694 “681 “669 -658 -648 -638 “628 
q 269-242 -220 -199 -182 -166 ‘153 
q/n 158 -139 -122 -108 -096 -085 -076 
Table V. 
Values of the index of the Radius m and of miq for different _ 
values of the Radius (2). 
R. Ob em. 10. 30. 30... 50.10... 20.8 
m 109. 143 2336. )S1 196 1:20 115 11 
mii 117 Of 60. A. 74 70: 08 
m/l8 1-11 79. 15. 43 40 66. 04 
m/l'9 1°05 10. $2) GS. 66. 623. 60. OF 
m/2 100... 7. 48 46. 43 60. 37. 
Kutter’s formula has been objected to by engineers on the 
ground that the estimation of his coefficient of roughness is practi- 
cally difficult and subject to a wide range of uncertainty. The 
1 These values can be regarded only as tentative. Sufficient ar ger 
mental data are not yet to hand to permit of the exact amount of the 
index being known. 
2 These values can only be regarded as tentative. The experimental 
data do not yet admit of m being accurately determined. m is very 
probably also a function of n. 
