VOL. XL.} PHILOSOPHICAL TRANSACTIONS. 141, 



N. B. Three things are to be remarked in this case: 



First, That when the angle made by the prop and the horizontal line, con- 

 tained between the centre of motion and the foot of the prop, is acute, as in 

 the last experiment, there is always a maximum: whereas when the same angle 

 is obtuse, there is no positive maximum; for then the pressure continually in- 

 creases, the nearer the prop is to the centre of motion. 



Secondly, That when the angle of the prop with the horizon is acute, as in 

 the last experiment, the bar, or long and heavy body, can be raised by applying 

 the power or prop always with the same angle to the horizon, quite up to a 

 vertical situation. 



Thirdly, That the first case, which is when the prop is perpendicular to the 

 horizon, is only a particular case of this more general one. 

 Case IV, Is when the angle made by the prop with that part of the Learn con- 

 tained bettveen the point to which it is applied, and the centre of motion, is 



given, either acute or obtuse. 



As the expression of the power in this case, is fully as intricate as in the last, 

 the Doctor gives only one example or experiment; and, for the greater satisfac- 

 tion of those that see it, he chose that in which the pressure is in its maximum. 

 He supposes, as before, the angle made by the prop, still 10 inches long, with 

 that part of the beam contained between the point to which it is applied, and 

 the centre of motion, to be acute, and of 6o°; then the maximum of pressure 

 will be, when the part of the beam intercepted between the centre of motion 

 and the upper end of the prop is 12 inches -rVo-; the bar is then elevated about 

 50° 1 3', and the horizontal distance between the centre of motion and the foot 

 of the prop, is then 1 1 inches -[Vo- 



N. B. Observe also in this case, as in the last. 



First, If the angle made by the prop, and the part of the beam intercepted 

 between the point of application and the centre of motion, is acute, there will 

 always be a maximum. The contrary will happen, if that angle is obtuse. 



Secondly, If the angle i* acute, the bar cannot be raised up to a vertical 

 situation by applying the power or prop constantly with the same acute angle; 

 but it may be raised quite up, if the angle of ihe prop with the beam is obtuse. 



Thirdly, The second case is but a particular case of this general one. 



The Apparent Times of the Immersions and Emersions of Jupiter''s Satellites, 

 for the Year 1739, computed to the Meridian of the Royal Observatory at 

 Greenwich. By James Hodgson, F. R. S. N" 445, p. 69. 



These calculations are omitted for the same reasons as before. 



