THE PHYSICS OF GOLF 27 



experimentally by Magnus in 1852 but already made clear by Newton in 

 1666, that, when a spherical ball is rotating and at the same time advancing 

 in still air, it will deviate from a straight path in the same direction as that in 

 which the front side is being carried by the rotation. Thus (to quote Tait) 

 " in topping, the upper part of the ball is made to move forward faster than 

 does the centre, consequently the front of the ball descends in virtue of the 

 rotation, and the ball itself skews in that direction. When a ball is undercut 

 it gets the opposite spin to the last, and, in consequence, it tends to deviate 

 upwards instead of downwards. The upward tendency often makes the path 

 of a ball (for a part of its course) concave upwards in spite of the effects of 



gravity " 



This last sentence contains the germ of the whole explanation ; but it 

 was not developed by Tait till four or five years later. Neither here nor in 

 any of his writings on the subject is any rash statement made as to the greatest 

 possible distance attainable by a well-driven golf ball. In his first article " On 

 the Physics of Golf" (Nature, Vol. XLII, August 28, 1890) Tait calculates by an 

 approximate formula the range of flight of a golf ball for a particular elevation 

 and various speeds of projection, the ball being assumed to have no rotation. 

 In this way by comparison with known lengths of " carry " he finds a probable 

 value for the initial speed of projection. He also points out that, to double 

 the " carry," the ball because of atmospheric resistance must set out with nearly 

 quadruple energy. About a year later (Sept. 24, 1891, Nature, Vol. XLIV, 

 p. 497), he treats more particularly of the time of flight. He finds that, 

 although we may approximate to the observed value of the range of a well- 

 driven ball by proper assumptions as to speed and elevation, it is impossible, 

 along those lines, to arrive at anything like the time of flight. The non-rotating 

 golf ball will according to calculation remain in the air a little more than half 

 the time the ball is known from experience to do. "The only way of 

 reconciling the results of calculation with the observed data is to assume that 

 for some reason the effects of gravity are at least partially counteracted. 

 This, in still air, can only be a rotation due to undercutting." 



Thus he comes back to the rotation of the ball as the feature which not 

 only explains the faults of slicing, pulling and topping, but is the great secret 

 of long driving. When the rotation is properly applied as an underspin about 

 a truly horizontal axis, the ball goes unswervingly towards its goal ; but, when 

 owing to faulty striking the axis of rotation is tilted from the horizontal one 

 way or the other, there is a component spin about a vertical axis and the ball 



42 



