NEWTON S PRIXCIPIA. 369 



being nearly the same as that given by the ordinary Hy- 

 drodynamic theory. Thus in one of Baily s brass 1- inch 

 sphere, the several parts of n were, for buoyancy 1, for 

 inertia, on the common theory, 5 additional for inertia on 

 account of internal friction -202 correction for wire -012 

 correction for confined space -032 total 1-746. Kesult 

 of experiment, 1 755, error y-i- T . 



(4.) In the fourteenth volume of the Edinburgh Transac 

 tions there will be found an interesting account of some 

 experiments by Scott Russell on the resistance experienced 

 by floating bodies in their progress through the water. As 

 the object was to determine the resistance to ships, the 

 experiments were conducted on a large scale, and the 

 bodies used were vessels of 31 to 75 feet long. The ve 

 locities varied from 3 to 15 miles an hour. Two points 

 are worthy of notice in these experiments. 



1. The Emersion of the solid body from the fluid. The 

 ship does not draw as much water when it is in motion as 

 when it is at rest. This is manifestly caused by the re 

 solved part of the resistance in a vertical direction. 



2. The motion of the boat does not excite currents in 

 the water, but generates waves. These waves travel to 

 great distances with a velocity independent of the form of 

 the vessel and, when freely moving, equal to the square 

 root of the product of the depth of the water and gravity. 



The position of the boat relative to these waves was 

 remarkable. Calling h the depth of the water, the ve 

 locity of a &quot;free&quot; wave will be * gh; let v be the velocity 

 of the boat. If v be less than ^gh, the wave will have a 



tendency to travel a little quicker than the boat, and it 

 was observed that the accumulation of all the waves ge 

 nerated by the boat formed an elevation at the prow and 

 a depression at the stern. Thus the vessel rode on the 

 posterior side of a &quot; forced wave,&quot; with its prow elevated 

 above its stern. If v be greater than ^gh, opposite phe- 



B B 



