220 Native Seleniuret of Lead and Sulphur et of Selenium. 



served this comet it was very near the ecliptic. As the wea- 

 ther will soon be more favourable, plenty of good opportu- 

 nities may be had of tracing its apparent path. The dark 

 nights will render it still more distinct, independent of its 

 nearer approach towards the earth. 



About three years ago, I discovered a small comet in the 

 Great Bcar^ with the same telescope, which I never observed 

 noticed in any of the journals, though visible for some weeks. 



Whatever further remarks I may be enabled to make, under 

 the privation of health, I will send you. 



I am your obedient servant, 

 Ipswich, 18th September, 182.5. J. AcTON. 



P. S. Right ascension 54*30, North declination 10-10, when 

 last seen. 



To the Editor of the Philosophical Magazine and Journal. 

 Sir, 



I hasten to communicate to you, that on the 15th inst. 

 being at Hartfield in Sussex, I perceived, about midnight, 

 during a very clear interval, a luminous phaenomenon with 

 which I was unacquainted, in the right shoulder of the Bidl. 

 On looking at it with a four-feet refracting telescope, it ap- 

 peared to be a comet, with a tail of considerable length, and 

 a nucleus about the apparent size of a star of the third or 

 fourth magnitude. Being just on the point of leaving home, 

 I did not make any further observations on it. Any colla- 

 teral remarks of your correspondents will be interesting. 

 I have the honour to remain, yours, &c. 



Sept. 23, 1825. T. FoRSTER. 



PLANETARY ANALOGIES. 



The ratio of the periodic times of any two planets, divided 

 by the ratio of their mean distances, is equal to the inverse 

 ratio of their projectile forces, or equal to the 4th root of the 

 inverse ratio of their gravitating forces, and which is constantly 

 equal to the square root of the ratio of their mean pi-opor~ 

 tional distances, — Required, a Demonstration ? 

 Sept. 1825. AlfreO/ 



NATIVE SELENIURET OF LEAD AND NATIVE SULPHURET OF 

 SELENIUM. 



*• As Piofessor Stromeyer has favoured me with a copy of 

 his and Professor Hausmann's paper on a native seleniuret 

 of lead, which was lately read before the Royal Society of 

 Giittingen, I beg leave to send you a notice concerning it. 

 The mineral was sent by M. Bauersachs, of Zellerfeld in the 



Hartz, 



