Section I IL, 1896. [ 4S ] Trans. R. S. C- 



\Y.—The Betermhiation of the Coefficient of Discharge for Sharp-edyed 

 Orifices: and an Investigation of the Force of Impact of a Half- 

 inch Jet on Va7ies of Various Forms. 



By J. T. Farmer, B.Sc. 



(Read May 21, 1896.) 



The object of this paper is to give an account of the piii'pose, the 

 means and methods of carrying out, and the results of experiments on 

 important phenomena in the subject of Hydraulics, The experiments 

 were made in the Hydraulic Laboratory at McGill University, Montreal, 

 where very comiDlete apparatus, especially designed under the direction 

 of Prof. Bovey, is available for such work. 



The main feature of the apparatus is an experimental tank, square in 

 section, 28 feet in height and having a sectional area of 25 square feet. 



One very important condition aimed at in designing this tank was 

 to obtain as nearly as possible the standard conditions of flow which 

 would exist in the ideal case of water starting from absolute rest. In a. 

 tank of finite proportions there must always be a certain amount of dis- 

 turbance of the stream-lines, due to the water which is constantly being; 

 led in to take the place of that discharged. Special precautions have 

 been taken in this case to reduce the disturbing effect of the incoming 

 water to a minimum. Originally the water was led in by means of a pipe, 

 and rose placed just below the surface of the water. This was the ar^ 

 rangement adopted in a course of experiments made by Prof. Bovey in 

 1894-5. It was afterwards thought that better results would be obtained 

 if the water were led in from underneath, and the necessary alterations 

 were therefore made. The water, in the series of experiments now de- 

 scribed, was admitted, in the first place, into a chamber some 12 inches, 

 high in the bottom of the tank. A false bottom with a number of per- 

 forations separated this chamber from the main portion of the tank, and 

 in passing through these perforations the flow of the water would be- 

 distributed over a large area, and the motion at any particular point 

 redviced to a minimum. 



Special attention was paid to the necessity of making the inside of 

 the tank perfectly flush, so that there should be no obstruction in the 

 way of the stream-lines. To this end, the flanges by which the cast iron. 

 sections of the tank were bolted together were placed on the outside. 



A simple and ingenious valve arrangement was designed b}' Mr. 

 "Withycombe, foreman of the testing laboratory, which fulfilled the re- 

 quirement of presenting a perfectly flush surface on the interior, and also 

 enabled the orifices to be rapidly changed when desired, without lowering 



