23y 



form, the rise is proportional to the square of the velocity, in ac- 

 cordance with an experimental result obtained by Mr Russell. 

 This inquiry is not pursued farther in that paper (though I believe 

 it may be done according to the method here employed), the im- 

 mediate object in view being to gain confidence for the particular 

 process of reasoning adopted, by explaining to a considerable ex- 

 tent a fact which had not before been shewn to depend on received 

 mechanical principles." 



On examining Professor Challis's reasoning in the paper referred 

 to, and divesting it of its technical form, it appears to be this; — 

 that if you suppose the bow of a vessel to be of a spherical form, 

 or what nautical men term " a spoon bow," and conceive it drawn 

 through the water rapidly, the force of impact of the bow and the 

 water may be resolved into two parts, one of which tends to throw 

 the bow upwards, and being a given part of the whole resistance, 

 tends to throw it up with a force proportional to the square of the 

 velocity. 



In other words, Mr Challis has expressed in mathematical terms 

 what was at that time the prevalent and vulgar error on this sub- 

 ject. It was early supposed by those who witnessed the phenomena 

 referred to, that the bow of the boat rose in the manner Professor 

 Challis conceives, and, as the immediate inference from this, it was 

 considered that the boat whose bow was most nearly of the spoon 

 form would be that which, according to these views, would rise 

 most and have least resistance ; but, on the contrary, on building 

 boats of this form which should have the greatest emergence and 

 least resistance, according to the view adopted by Professor Challis, 

 it turned out that they were the very opposite, and that, on alter- 

 ing them to the form of the most acute wedge in which, by Mr 

 Challis's method, they could have no emergence, and no diminution 

 of resistance, they became the very reverse of what had been sup- 

 posed. Thus it occurred that a very simple experiment put them 

 right, and overturned the views of Professor Challis. 



The effect which Mr Challis conceives he has accounted for is 

 one of a totally different nature, and indeed the opposite of what 

 he has imagined. It is well known to every one at all acquainted 

 with the motion of boats, or the theory of their construction, that 

 a full or spherical,bow is violently raised up when propelled at high 

 velocities ; but it happens unfortunately that the stern is violently 

 depressed, while the resistance is greatly increased. Now Profes- 

 sor Challis's view would require the vessel to be wholly raised 



