202 



HYDKAULICS AND ITS APPLICATIONS 



Professor Unwin, neglecting the small effect of temperature change at 

 velocities above the critical, wrote this formula ip the form 



d* 



and deduced values for/, n, and x, from the results of experiments made 

 by many different observers, and on pipes ranging in diameter from 

 2 inches to 48 inches. 1 He found that x is always greater than unity, 

 increasing with the diameter between the limits 1*127 and 1*890. 

 The following are Un win's mean values for/, ?i, and x. 



G. M. Lawford? comparing the latter formula with many recorded 

 observations of more recent date, states that by writing the formula in 

 the form 



0254 I v 1 ' 81 

 2 g d 1 ' ' 



and by giving k the following values, the necessity for altering the value 

 of x with increasing diameter is obviated, while the formula. gives good 

 results for asphalted pipes of all diameters from 3 inches to 48 inches. 



1 "Industries," 1886, vol. 1, p. 51 and seq. 



a " Proceedings Inat. Civil Engineers," vol. 163, p. 297. 



