486 Transactions. 



The dots represent a series of sixty-six observations made by Moritz on 

 wood stave pipe recorded in the " Transactions of the American Society of 

 Civil Engineers," vol. 74 (1911). The pipe-diameters range from 18 in. to 

 55f in., and velocities from a fraction of a foot per second to 5-874:. These 

 experiments are noteworthy on account of the extent of and care exercised 

 in carrying out the experiments. 



Regarding the results, it will be seen that quite a number of the dots 

 are on the standard curve for smooth pipe, and otherwise by their disposi- 

 tion strengthen the evidence in favour of the curve a being the true law for 

 smooth pipe. 



Regarding these results, it may be truly said that under favourable 

 circumstances a wood stave pipe may be treated as a smooth pipe, and the 

 resistance truly represented by curve a in the figures. The other curves 

 have been drawn in fig. 3 — viz., h and c — -the former a sort of mean curve, 

 and the latter an outside or superior limit after neglecting what appear 

 to be errors of observation. These curves have been transferred to fig. 1, 

 and may be identified by the same lettering. The conclusion so far as regards 

 wood stave pipe is that the value of 1/C^ lies between 



•00801 ( -^ j + -000028 



and 



-00801 {-) + -000052, 

 whilst the mean or commonest value may be taken as 



•00801 ( -^ I + -000042. 



It is reasonable to assume that asphalted pipes of any material wUl 

 yield the same results as wood stave pipe, provided the joints are well made 

 and even, and that there are no projections of any kind such as rivet-heads 

 or straps, and that the asphalting lies smoothly and evenly. The common 

 defect in asphalted pipes is that the pipe has been immersed in an asphalt 

 mixture having too low a boiling-point, with the result that the asphalt 

 coating is of uneven thickness and corrugated, thereby considerably increasing 

 the resistance. Cast-iron pipe or solid-drawn or welded iron or steel pipes 

 should, if this asphalting is properly done, yield results within the limits 

 given for wood stave pipe. 



Whilst no certain conclusion can be drawn as to the correct expression 

 of the law of resistance of rough pipes, we can say the whole range or 

 experience lies bounded by the curves a and a curve similar to and not far 

 different in shape and position from curve e, and as an instance of the appli- 

 cation of the curves of fig. 1. Suppose that the conditions are such that 

 the value of log vd/v is 7, and that we wish to know the value of 1/C^ for 

 riveted pipe, we can be certain it is not less than -000056, whilst the 

 probability is that it is not less than -00008 nor more much than -000126, 

 whether curves c and e are correctly drawn or not, or whether the equations 

 given for these curves are right or wrong, whilst there is a preponderance 

 of experience in favour of a value of -000096, which is found on curve d. 



Applying the same reasoning to a wood stave pipe, and assuming that 

 the value of log vd/v is 7 as before, the value of 1/C^ cannot be less than 

 -000056, and is not likely to exceed -00008, whilst the probable value is 

 -00007. 



