of Processes in the Fine and Useful Arts. 355 



^. Account of a method of measuring (he resistance of fluids to bodies paS' 

 sing through them. By James Walker, Esq. F. R. S. Edin. 

 As it has been demonstrated that the resistance from friction to a carriage 

 upon a road or rail-road is the same at all velocities, Mr Walker was de- 

 sirous of ascertaining the strain upon a boat when moving at different ve- 

 locities. This experiment was made in the middle of the East India Im- 

 port' Dock, (1410 feet long, 560 wide, 924 deep,) so that there was no re- 

 sistance from the sides or bottom of the dock. A spring weighing machine 

 was fixed near the bow of the boat, the dial laid horizontally so as to be easily 

 seen by a person on board ; one end of a line | of an inch in diameter 

 was attached to the back of the spring, the other end was carried ashore 

 and attached to a rock or barrel, 3 feet in diameter, the frame of which 

 was firmly fixed in the ground, and the handles of sufficient length for the 

 necessary number of men to turn the barrel. The velocities were calcula- 

 ted from the time of passing through 176 yards, or ^^ of a mile, but to 

 obtain uniform velocity, the boat was at each experiment drawn over twice 

 the length, and the 176 yards taken in the middle of the distance by two 

 marks upon the line. The line between the two marks coming to the edge 

 of the dock was carefully noted by a person stationed there for the purpose. 

 Three persons at least were on board the boat, one to read off the strain 

 shown upon the dial every 2 seconds ; one to write them down, and a third 

 to steady the boat. An exact uniformity of motion by the men at the 

 handles was obtained by a little practice, by means of a pendulum varying 

 in length (as a quick or slow motion was required), hung up in sight of 

 the men, by the oscillations of which they regulated the revolution of the 

 handles. The weights marked by tHe index of the dial measured only 

 the resistances to the boat- The following were the results obtained with a 

 full built boat loaded with 2 tons 2 cwt- exclusive of the men. The length 

 of the boat on the surface of the water was 1 8^ feet, its breadth 6 feet, its 

 depth of immersion 2 feet, the whole depth of the boat being 3 feet, leaving 

 one foot above water, the greatest immersed cross section 9 feet. 



TABLE I. 

 No. of seconds in Velocity per Observed resist- Calculated resist- 

 passing 176 yards, hour in Miles, ance, or strain in ance, No. 6 being 



lbs. on Dial. the standard. 



1 124 2.903 15.75 15.04 



2 85 4.235 39.50 32.01 



3 146 2.465 " 10.00 10.85 



4 140 2.571 11.00 11.80 



5 145 2.483 11.00 11.00 stand. 



6 140 2.571 12.00 11.80 



7 120 3.000 14.00 16.06 



8 120 3.000 14.00 16.06 



The average resistance of Nos. 7, 8, and 10, (low velocities) is 9.41 lbs. 

 . and the corresponding velocity 2.529 miles. The average of Nos. 1 and 2 

 -(high velocities) is 42.59 lbs. and the velocity per hour 4.529 miles. The 



calculated resistance in these cases would be 

 : For low velocities 22.04 instead of 28.07 

 high 38.1 1 42.59 



