THE LAWS OF FLUID RESISTANCE. 



BY W. FKOUDE, ESQ., LL.D., F.R.S. 



I PROPOSE to consider those principles of fluid motion which 

 influence what is termed the " resistance " of ships. By the 

 term resistance, I mean the opposing force which a ship ex- 

 periences in its progress through the water. Considering 

 how great an expenditure, whether of sail or steam power, is 

 involved in overcoming this resistance, it is clearly most 

 important that its causes should be correctly appreciated. 



This subject is a branch of the general question of the 

 forces which act on a body moving through a fluid, and has 

 within a comparatively recent period been placed in an 

 entirely new light by what is commonly called the theory 

 of stream-lines. 



This theory as a whole involves mathematics of the highest 

 order, reaching alike beyond my ken and my purpose ; but 

 so far as we shall have to employ it here, in considering 

 the question of the resistance of ships, its principles are 

 perfectly simple and are easily understood without the help 

 of technical mathematics ; and I will endeavour to explain 

 the course which I have myself found most conducive to its 

 apprehension. 



In order, however, to show you clearly what light the 

 theory of stream-lines has thrown on the question, I must 

 first describe the old method of treating it, which is cer- 

 tainly at first sight the most natural one, and we shall thus 

 see what germs of truth that method contained, and how 

 far these were developed into false conclusions. 



