478 POPULAR LECTURES AND ADDRESSES. 



mechanical grounds that traction in a canal can 

 compete for any considerable speeds with traction 

 on a railway. Taking again some of the figures 

 already given, a boat weighing 10,239 Ibs. required 

 112 Ibs., or about i-iooth of its weight, to drag it 

 at 4f miles an hour. So that to drag a boat at 

 that moderate speed took the same force as would 

 be required to drag it on wheels up an incline of 

 i in IOO, supposing there to be no friction in the 

 wheels on a railway. But at the higher speed of 

 9 miles an hour, taking advantage of the com- 

 paratively smaller force due to having passed the 

 velocity corresponding with the long wave, we have 

 250 Ibs., which divided by 10,239 is about I in 40 ; 

 so that the force required to drag the boat along 

 at the rate of 9 miles an hour was what would be 

 required to drag it on wheels up an incline of 

 i in 40. Sad to say, I am afraid the wheels have 

 it in an economical point of view. 



Ship Waves at Sea. I must now call your 

 attention to the most beautiful, the most difficult, 

 and in some respects the most interesting part of 



