MR RUSSELL'S RESEARCHES IN HYDRODYNAMICS. 109 



DESCRIPTION OF PLATES II. AND III. 



PLATE II. 



Fig. (I.) Represents the form given to the surface of a fluid by the motion of a floating body. The bed 

 of the channel was nearly of the form given in Fig. F, which is a transverse section taken at right 

 angles to the direction of motion of the floating body. The arrow at the stem of the vessel indi- 

 cates the direction of the moving body, and on each side a dotted line shews the place of the fluid 

 when at rest. The anterior wave at the bow of the vessel swells above and beyond the line of 

 rest, the stern depression falls below and within it, the summits of the stern waves of replacement 

 also protrude beyond and above it. The summits of the waves of unequal displacement, due to the 

 improper form of the vessel, extend from it towards the banks, and give rise to undulations of the 

 second order on the terminal line of the fluid. 



Figs. (2.) (3.) and (4.) are the observed forms of the great primary wave of the fluid, in the channel of 

 which the form is given in Fig. E, and in which the mean velocity of the wave is 8 miles an hour. 



Figs. (5.) (6.) and (7.) are observed forms of compound waves which were afterwards analyzed, and 

 gave the elementary and simple forms of Figs. (2.) (3.) and (4.) The outline represents the com- 

 pound wave, the inner lines indicate the analysis. 



Figs. A, B, C, D, E, and F. are sections of channels in which waves were propagated and other ex- 

 periments made, and to which reference is made in the paper. 



PLATE in. 



Figs. (1.) (2.) (3.) and (4.) are projections of the forms of vessels made the subject of experiment 

 They are simply fore-shortened, so as to diminish their length in the ratio of 3. : 1, or they are 

 projected on an angle sin — ^ = ^, so that the transverse sections are diminished in the ratio of the 

 cosine of that angle, the dimension of depth remaining unchanged. The dotted lines at the 

 sides are drawn for each six inches of immersion, so that a line may be drawn across the whole 

 of each vessel at the depth of immersion given in the tables, for the purpose of shewing the parts of 

 the vessel below and above the surface of the fluid. Below the projection are given the unpro- 

 jected water lines for each six inches of immersion; the lines of the bow are placed above those of 

 the stern. 



Fig. (5.) consists of the transverse sections, longitudinal section, water lines, and elevation of the Ex- 

 perimental Skiff" of 1834, P', P" and P'", the position of the tube of Pitot. Ti, Tg, T3, Pg, Tj, Tg, 

 glass gauges of immersion. 



Fig. (6.) Shews the improved mode of obtaining a continuous moving force as used in 1835. The power 

 of horses is not applied directly to the object to be moved, but acts on the end of a rope at A, which 

 rope extends directly from A to a fixed pulley at B, whence it passes to the summit of a pyramidal 

 structure 75 feet high round another fixed pulley C, descends to a pulley at the weight D, and 

 passing round it returns to a second pulley at C, descends once more to B, and is finally attached 

 to a dynamometer at E, the bow of the vessel. The power of the horses is therefore used to sustain 

 the weight, while its gravity overcomes the resistance of ^he fluid. An assistant at the foot of the 

 pyramid prevents the weight from turning round, and a second weight F may be used for accelera- 

 tion previous to the commencement of the observations. 



