BiRKS AND Webb. — Resistance of Earth Connections. 481 



possible leads. This question will be the subject of further investigation 

 as opportunity ofiers. 



To conclude, the observations here set out demonstrate the uniformly 

 high resistance of earth in the country investigated. Comparison with 

 published data accentuates the contrast with the average values found 

 elsewhere. It is not suggested that this is the only place of the kind, but 

 it is e\Tident that some circumstance is responsible for the abnormal high 

 resistances. 



A further item which points to a high resistance of soil in the district 

 is the fact that very little electrolysis of waterpipes, &c., has been noted. 



Although the dryness of the shingle plain may be responsible for some 

 of the high resistances, it cannot account for their persistent occurrence. 

 Christchurch and environs is extensively suppUed with artesian water which 

 itself is almost pure, containing the very lowest percentage of salts or 

 impurities of any kind. Since pure water has such a high resistance, this 

 may account for the high " earth " resistances encountered. 



Art. XLIX. — Resistance to the Flow of Fluids through Pipes. 

 By E. Parry, M.I.E.E., Assoc.M.Inst.C.E. 



\^Read before the Technological Section of the Wellington Philosophical Society, 10th 



Novetnber, 1915.] 



The present work is the result of an effort to express the resistance offered 

 by rough pipes, as distinct from smooth pipes, to the flow of fluids in terms 



of — where v is the mean velocity of flow, d the diameter of the pipes, 



and V the kinematic viscosity of the fluid. 



The investigation was prompted by the publication in the " Philo- 

 sophical Transactions of the Eoyal Society A," vol. 214 (1914), of Stanton 

 and Pannell's experiments upon smooth pipes, and more particularly by 

 the publication in the " Proceedings of the Royal Society A," vol. 91 (1914), 

 of Professor Lees's discussion of those experiments. The latter work con- 

 tains an admirable historical resume of the subject, so there is no need to 

 dwell further upon that aspect than to state that the resistance offered by 

 a viscous fluid of any kind flowing in a circular pipe is proved by Stoker, 

 Helmholtz, Rayleigh, and Reynolds from dynamical considerations to be a 

 function of the expression vd/v. 



Below a certain critical value of the velocity the resistance is purely 

 viscous, and the function mentioned is a simple one, \'iz., — 



.^=«C^) '^' 



where R is the resistance per unit of surface, p is the density of the fluid, 

 a is a. coefficient, the other values having the same significance as before. 



Above the critical value of the velocity the resistance is apparently 

 partly viscous and partly an inertia effect, and the relation between the 

 elements a complex one ; so much so that the probability is that it cannot 

 be exactly expressed by any formula ; neither is a formula an absolute 

 necessity, though an approximate formula, if obtainable, is undoubtedly a 

 convenience. 



1&— Trans. 



