of Fluids, compared with the best Experiments. 261 



ordinates of two curves, these curves would cross five times at 

 unequal distances in the range. 



Explanation of the Plate. 



Fig. 1. A body moving in the direction AB. The collision 

 and line of reaction of a filament of the fluid from the oblique 

 surface of its fore-part are indicated by faint lines, with dotted 

 lines to represent the composition and reduction of the forces. 

 The motion of the fluid after the body is also shown by lines 

 of a light tint. The dotted rectangle is equal to the oblique 

 parallelogram, but the motion of the fluid is less as the obli- 

 quity increases. 



Fig. 2. Represents the plan of the body used by the French 

 Academicians in their experiments ; the head was altered to 

 different angles, but the form of the after-part remained the 

 same in all their experiments. 



Fig. 3. is to show the effect of moving a plane surface in a 

 fluid when placed obliquely in respect to the direction of its 

 motion ; and it is obvious that the edge of the plane must have 

 a sensible effect on both the direct and minus-pressure. 



Fig. 4. 5. and 6. are, a sphere ; a cylinder, with the after- part 

 a hemisphere ; and a cylinder with the fore-part a hemisphere ; 

 having the characters used for calculation annexed to their 

 respective lines. 



From the flat end of fig. 5. the stroke and reaction being 

 in the same direction, the fluid cannot move laterally till the 

 central pressure so far exceed that on the more remote parts as 

 to cause the proper quantity of lateral motion ; or till a portion 

 of the fluid accumulates before the body : but the portion ac- 

 cumulated being a fluid, the forces must produce the same effect 

 as if each filament were struck and reflected by the solid plane. 



Fig. 7. The plan of a body formed by segments of circles, 

 with the characters annexed to the lines. When the radius is 

 half the breadth, the form becomes a prism terminating in semi- 

 cylinders at the ends (as fig. 8). 



Fig. 9. and 10. are to show how the two motions of the fluid 

 interfere when the fore- and after-part are separated by a thin 

 edge only. In the hemisphere (fig. 9.), the resistance is in- 

 creased by the fluid displaced by the fore-part preventing the 

 fluid from following behind the body. In fig. 10. the reflected 

 fluid from the fore-part in some degree facilitates the motion 

 of the following fluid. 



It will be evident to any one who examines the preceding 

 paper, that it must have cost me a great deal of labour ; and 

 in consequence I was desirous of presenting it to the Royal 

 Society. But finding that I must sacrifice all claim to new 



theoretical 



