8 Derivation ofove of the Equations in 



9-835 gr. of red lead had aftbrded -29 of oxvgen and g-545 

 of yellow oxide, or 8-855 of lead, which had been united 

 with -98 of oxygen. Now 8-835 : 98 = 100 . ! I'Ol \ con- 

 sequently 100 parts of lead, in becoming red lead, take up 

 irOT of oxygen, and this oxide consists of 90 parts of lead 

 and 10 of oxygen. 



C. Brown Oxide of Lead. 



It is well known that red lead, digested with nitric acid, 

 affords a brown oxide of lead. While the nitric acid dis- 

 solves the yellow oxide and reduces a part of the red to 

 yellow, it leaves the brown oxide undissidved, together 

 with a quantity of impurities, especially sulphate of lead 

 and silica. 



Five gramines of brown oxide of lead, freed by washing 

 from all the nitrate which had adhered to it, and dried ia 

 a sand-bath, with a heat capable of melting tin, were 

 ignited in a weighed dish of platina, and lost '325 gr. of 

 oxygen. The remaining 4*675 gr. of yellow oxide, dis- 

 solved in vinegar, left behind some sulphate of lead and 

 silica, which when ignited weighed together '13 gr. 

 Th« remaining 4-515 gr. of yellow oxide contain '33 gr. 

 of oxygen, a quantity differing only by '005 gr. from 

 that which the brown oxide had lost by ignition. Con- 

 sequently !00 parts of lead, in order to be converted into 

 brown oxide, require twice as much oxygen as is contained 

 in the yellow oxide, and the brown oxide consists of 

 Lead 86-51 lOO'O 



13-49 15-6 



100-00 115-6 



It seems lo follow as the result of these experiments, 

 that lead, in its three different degrees of oxidation, takes 

 up oxygen in quantities which are related in the proportions 

 of 1, i|, and 2. 



[To be continued.] 



II. Derivation of one of the Equations in Laplace's 



" Mecanique Celeste.'" 



To Mr. Tilloch. 



Dear Sir, JL he accompanying paper I had from my 

 particular friend and successor in the mathematical school 

 of Dumfries, Mr. Thomas White. That school I esta- 

 blished about 40 years ago, and Mr. White has taught it 



with 



