SOG Proceedings of PJulosophical Societies. [Apftit, 



Sulphuret of lead 57'269 



Sulphuret of copper 40"85O 



Sulphuret of iron 2" 1 90 



100-309 



This ore, supposing the iron to be accidental, consists of one 

 integrant particle of sulphuret of lead combined with two integrant 

 particles of sulphuret of copper ; and hence the Doctor was in- 

 clined to consider it as a new species of lead-ore, of little value 

 however in a metallurgic point of view. 



At tliis meeting, also, there was presented to the society a branch 

 of mimosa decurrens, containing several bunches of flow-ers, the 

 first time they have been produced in this country. The plant is in 

 the fine conservatory at Milburn Tower, the seat of the Ambas- 

 sador Liston ; it is fifteen feet high, and has been thrown into a 

 flowering state by the judicious management of Mr. Joseph Smaill, 

 the gardener, who checked its growth, by cutting some of the 

 roots, and by substituting a proportion of sand for rich earth. 



IMPERIAL INSTITUTE OF FRANCE. 



Account of the Labours of the Class of Mathematical and Physical 

 Sciences of the Imperial Institute of France during the Year 1813. 



(Continued from p. 234.) 



Memoir of M. Burckhardt on the Quantity of Matter in the 

 Planets. 



The formulas of M. M. Lagrange and Laplace enable us to 

 assign for any epoch the situation and dimensions of the planetary 

 orbits. Mathematically speaking, the problem is resolved. The 

 arbitrary constant quantities are mostly determined with a sufficient 

 degree of accuracy for these researches. We are acquainted even 

 with the quantity of matter in those planets which have satellites, 

 as is the case with Uranus, Saturn, Jupiter, and the Earth ; but 

 Mars, Venus, and Alercury have no satellites. We have no other 

 means of determining the quantity of matter in them than the 

 alterations which they produce in the eccentricities and inclinations, 

 or the equations which they give for the movements of the aphe- 

 lions and nodes. But these variations are extremely slow. Good 

 observations go no further back than 60 years. There remain only 

 the periodic equations of the longitude. These equations are not 

 greater; but their periods are'shorter. Half a period is sufficient 

 to obtain a double effect, since it is alternately positive and negative. 

 The moon is almost in the same situation with Venus. Notwith- 

 standing the assistance drawn from the tides and from the nuta- 

 tion, we have not yet an exact knowledge of the quantity of matter 

 in our satellite. 



Yet unless we adopt at least a hypothetic value for these unknown 

 quantiticSj it is impossible to have exact tables of tlic apparent 



