154 



Royal Society. 



JSxperiments in my House. 

 After many failures the apparatus became tolerably etficient, with 

 a pendulum of 68*7 inches, as deduced from the vibrations, 22*64 in 

 a minute. The balls used were a prolate spheroid weighing 6^ lbs., 

 and a globe weighing only K^lb. I have obtained the best results 

 with the smaller weight. The suspensions have been silk, gutta 

 percha, and various contrivances of points and sockets of agate, brass 

 and steel. The best results have been obtained with gutta percha, 

 and sockets of agate and steel. The arc mostly used was from 16 

 to 20 inches. The experiments were seldom continued beyond half 

 an hour. By that time the chord of vibration was reduced to about 

 7 or 8 inches, and the errors of experiment were thought likely to be 

 too great, with so short a radius, if longer continued. The ball, in 

 whatever direction swung, presents the same face to the same side 

 of the room. 



From these experiments uncorrected for ellipse, we have, — 

 Exp. 6. 8. On N.E. and S.W.lineii±i?=13°-0inonehour. 



7. 9. On N.W. and S.E. linei2^55±iLi? = io°-88. 



I have since made a great variety of experiments with this apparatus, 

 which, notwithstanding the theoretical and practical disadvantage of 

 working with so short a pendulum, I hope to render accurately 

 effective, so that the angular deviation of the pendulum-plane may 

 become an ordinary and easy experiment. It should, however, be 

 tried in a glass case, and probably in vacuo. 



4. " Note on instantaneous Photographic Imaeres." By H. F. 

 Talbot, Esq., F.R.S. &c. 



Having recently met with a photographic process of great sensi- 

 bility, I was desirous of trying whether it were possible to obtain a 



