268 Professor Gordon on the Discharge of Water through Pipes. 



expected, it will be the proper time to introduce a bill into Parliament 

 for the improvement of these Registers. It would bo well, therefore, 

 that the Statistical Section of this Society should appoint a Com- 

 mittee to watch over the measure, and to take such steps as may be 

 necessary to forward it 



Mr. Gourlio communicated some observations on the natural 

 history of several species of British zoophytes, illustrated with speci- 

 mens; and Mr. Stenhouse drew the attention of the Society to speci- 

 mens of manna which he had obtained from different sea-weeds, in 

 accordance with the observations of Vauquelin andGaultier de Claubry. 

 Mr. Stenhouse stated that from the Laminaria saccharina he had 

 extracted as much as twelve-and-a-half per cent, of manna by means 

 of alcohol. 



The following communication was read. 



LV. — Test of Formula for Discharge of Water through Pipes. — 

 By L. D. B. Gordon, Regius Professor of Civil Engineering and 

 Mechanics. 



The formula which best represents the results of Provis's experi- 

 ments, as well as those of Hagen,* and the experiments of Dubuat, 

 that could be employed, as also of Couplet, is based upon the formula 

 originally proposed by Woltmann,t in which the height due to the 

 resistance in the pipes is made proportional to a certain power deduced 

 from experiments. The exponent 1-75 was deduced by Woltmann, 

 and is also the most probable exponent according to the experiments 

 above mentioned. 



It was advisable, after assuming this exponent, first to determine the 

 head due to the velocity of discharge, and as this is expressed by a 

 member containing the second power of the velocity as factor, but quite 

 independent of the length of the pipe, only those experiments could 

 be used in which pipes of the same diameter were used but of several 

 different lengths, as in the experiments of Provis and Hagen, and certain 

 of those, for small pipes, of Dubuat ; and some of Couplet's for pipes of 

 even twelve to eighteen inches diameter. 



The equation of condition chosen then, was : 



I / c \ 2 1 _ 



1-75 



9 

 In which h = the head, due to the resistance in the pipes, c = the 



* Detailed in Poggendorff, vol. 36. 

 t Beitrage zur Hydraulischcn Architectur. Bd. I. 151. 



