Chase.] ^ [March 19, 



him to appoint delegates to Boston, he requested the Secre- 

 taries to send information to each of the Board of Officers 

 and to Dr. R. E. Rogers and to Mr. Wm. A. Ingham that he 

 nominated them as delegates to represent this Society and 

 assist on the 26th of May at the Centennial Celebration of 

 the American Academy of Arts and Sciences in Boston. 

 The meeting was then adjourned. 



Astronomical Approximations. IV. Nodal Estimation of the Velocity of 

 Light. By Pliny Earle Chase, LL.D., Professor of Philosophy in 

 • Haverford College. 



{Bead before the American Philosopliical Society, March 19, 1880.) • 



The accuracy of my approximation to the apparent semi-diameter of the 

 Sun* is confirmed by the following kinetic considerations, some of which, 

 though seemingly of great fundamental importance and character, liave 

 been generally overlooked. 



1. Matter has been usually regarded as composed of discrete particles. 

 This hypothesis enters even into the kinetic theory of gases. If it is 

 true, all force must be transmitted from particle to particle and time must, 

 therefore, be required to overcome the inertia of masses. 



2. Attraction and repulsion have been generally considered under the 

 influence of central forces, varying inversely as the squares of the distances 

 from the centres and, therefore, producing motions with variable velocity. 



3. Waves, orbital undulations, and other cyclical motions, are generally 

 propagated with uniform or nearly uniform velocit}'', although they are 

 often accompanied by subordinate movements with varying velocity. 

 Yariable velocities are often converted into uniform or nearly uniform 

 velocities, as in the case of conical pendulums, planetary rotations and 

 orbital revolutions. 



4. In all undulations, and in all cyclical motions through an undulating 

 medium, there are tendencies to synchronism. The synchronism may be 

 complete, producing equal cyclical motions in equal cyclical times ; or 

 nodal, producing harmonic series of cyclical motions Avhich are completed 

 in equal times. 



5. Newton showed that if a centripetal force varies as the distance of a 

 body from the centre, all bodies, revolving in any planes whatsoever, will 

 describe ellipses and complete their revolutions in equal times ; f that 

 bodies which move in right lines, running backwards and forwards alter- 

 nately, will complete their several periods of going and returning in the 



* Proceed. Am, Phil. Soc. xvili, 3S0. 

 t Principia, B. I, Prop. 47 



