ON HYDRAULICS AS A BRANCH OF ENGINEERING. 181 



and with twenty-four right angles, one third ; but did not seem 

 to observe any decided law. 



In several experiments tried on a great scale, the results 

 gave from one fifth to one sixth of the altitude for the fric- 

 tion. In the case of the Coniston main, which conducts the 

 water from the reservoir at Coniston to the castle of Edin- 

 burgh, the diameter of which is 41 inches, the length 14,930 

 feet, and the altitude 51 feet, it was proved by Mr. Jardine 

 that the formulae of Dubuat and Eytelwein approximated to 

 the real results very nearly ; and in some experiments made on 

 a. great scale by the author of this paper, these formulae were 

 found equally applicable. In several experiments made in the 

 year 1828, on the water-works at Grenoble, by M. Gueymard, 

 it was found that pipes of six and eight French inches in dia- 

 meter furnished only two thirds of the water indicated by the 

 formulee of M. Prony ; but when of nine inches diameter, the 

 formula approximated very nearly. In M. Gueymard's expe- 

 riment the altitude of the reservoir above the point of delivery 

 was 8*453 metres, or 27'73 English feet. The height to which 

 the water was required to be elevated was 5'514 metres, or 

 18 feet ; the volume of water required was 954 litres, or 33*6 

 cubic feet; the length of the pipe was 3200 metres, or 10498 

 feet. There were eight gentle curves in the system, but en- 

 larged beyond the average diameter of the parts of the pipe ; 

 from which it resulted that the height to which the water was 

 delivered was only two thirds of the height of the reservoir*. 



In the preceding short but imperfect history of the science 

 of hydraulics we have confined our attention to the experi- 

 mental researches that have been made on spouting fluids only. 

 In a future communication I hope to examine the state of 

 our knowledge of the natural phaenomena of rivers, and the 

 causes by which they are influenced ; at present it is extremely 

 limited, and although we have many works upon the subject, 

 very little seems to be known either of their properties or of 

 the laws by which they are governed. 



• According to M. Prony 's theory, the height raised would only have been 

 ■5-514 metres instead of 5-671 metres. The difficulty, however, of making ex- 

 periments on a great scale will always prove an obstacle to the right solution 

 of the question, in as much as it exacts that the pipe be of the same dia- 

 meter throughout, that is, perfectly straight, and free from bends, and the 

 charge of water invariable. For this purpose M. Prony has calculated Tables 

 showing the relation subsisting between the expenditure, diameter, length, the 

 total inclination of the pipes, and the difference of pressure at its extremities. 



