1814.] Experiments made at Greenland Dock. 49 



contain the weights necessary to put the body in motion. As It 

 was found that the motion of the body in the water was at first very 

 slow, compared with the velocity which it afterwards acquired and 

 preserved, an additional weight was made at first to act for some 

 time, in order to bring it the sooner to its maximum velocity ; but 

 it being found that when this weight suddenly ceased to act, a 

 tremulous motion was produced which interfered with the regu- 

 larity of the body's progress, a chain was substituted for the addi- 

 tional weiglit, which reaching the ground in succession, its action 

 was gradually withdrawn without producing any such injurious 

 effect. 



The time was measured by means of a pendulum clock, to which 

 there was attached a batten moving over a long horizontal frame 

 accurately divided into parts, and by means of a spring a pencil- 

 mark was left on the frame at tlie end of every second or interval 

 required. By this peculiar contrivance it was found easy to divide 

 a second into 1000 parts, and to determine the motion to the 1000th 

 part of a second, a degree of precision never before attempted, far 

 less obtained in any similar experiments. The apparatus underwent 

 successive alterations before it reached its greatest perfection ; and 

 on tliat account the earlier experiments are not entitled to the same 

 degree of confidence as those made at a later period. In the 

 following table the experiments are placed in the order in which 

 they were made. 



I. Bodies Floating on the Surface of the Water. 



1. A parallelopipedon of wood. Length, 42*198 feet. Breadth, 

 3-668 feet. Depth, ]'219 feet. Area of the end, 4-4;i3 feet : 



Velocity, 12 f. per second. Motive weight, 947'23 lbs. Avoir. 



2. A similar parallelopipedon of half the length : 

 Velocity 12 f. per second. Motive weight, 797'43 lbs. 

 6 155-y6 



3. The first parallelopipedon on its edge: 



Velocity per second, 12 f. Motive weight, I>39 74 lbs. 



4. The first parallelopipedon lengthened by adding a semicircular 

 end to each extremity : 



Velocity per second, 12 f. Motive weight, 693-1 lbs. 

 .5. A triangular piece of wood with its base foremost. Length 

 of perpendicular, 43*125 iett. Breadth, 4*7416 feet. Depth, 

 1-219 feet. Area of the base, 578 feet: 



Velocity j)er second, 12 f. Motive weight, 1041*70 lbs. 



6. The same triangle with its vertex foremost : 



Velocity per second, 12 f. Motive weight, 39550 lbs. 



7. A paralklopipcdon and triangle joined together, the parallelo- 

 pipedon foremost. Length of parallelogram, 10*333 feet. Breadth, 

 3*666 feet. Depth, 1219 feet. Area of the end, 4*4713 feet. 

 Length of triangle, 32- 79 feet : 



Velocity per second, 12 f. Motive weight, 801*95 lbs. 



