TRANSACTIONS OF THE SECTIONS. 47 



The increase, then, acquired by one atom of load, will, in the case of 

 the sulphate, be the sum of one atom of sulphur and four atoms of 

 oxygen (S'04), and, in the case of the nitrate, be the sum of two 

 atoms of azote and six atoms of oxygen (A^Og). Starting from the 

 atomic weight of lead, varying as already given, the following table 

 exhibits the varying experimental increments corresponding to S'04 

 and to A^Og : 



Greatest. Mean. Least. 



On LEAD one atom, 1295-27 1293*82 1292*65 



ItX CTCCtSG* 



r Greatest 601-41 601-02 600*67 



S'O^ <( Mean 600-73 600-34- 599-99 



L Least 600-19 599-80 599-45 



f Greatest 778-03 777-15 776-46 



A^Oo I Mean 777-51 776*64 775-94 



[Least 776-99 776*12 775-42 



Deducting 400* for the oxygen in the sulphate, and 600* for the 

 oxygen in the nitrate, we obtain the following atomic weights : 



Greatest. Mean. Least. 



Lead, 1 atom. ... 1295*27 1293*82 1292*65 



Sulphur, 1 atom. ... 201-41 20034 199-45 



Azote, 2 atoms. ... 178-03 176-64 175*42 



The differences between the experimental atomic weights of each of 

 these elements are 



Between mean and extremes. Between extremes. 



Lead +1-45 - 1*17 2-62 



Sulphur +1*07 - -89 1*96 



Azote (A2) +1*39 - 1*22 2*61 



These differences are considerable. They show that there is an un- 

 certainty of + 1* in the place of units, in each equivalent, oxygen being 

 assumed at 100*. From the manner in which the atomic weights have 

 been sought, the difference in the instance of sulphur is evidently due 

 partly to the variations found in the atomic weight of the lead, and 

 partly to the variation in the increase that lead acquires in becoming 

 sulphate ; and the difference in the instance of azote is due not only 

 to the same two variations, but also to the varying product of the sul- 

 phate from a given weight of the nitrate. What portion of the differ- 

 ences between the mean and each extreme is due to each of these 

 causes, in the equivalents of sulphur and of azote, appears in the fol- 

 lowing table : 



In sulphur. In azote. 



On account of the oxide +*68 — *54 +*87 — -70 



„ „ sulphate + -39 —-35 +-42 —-39 



„ „ nitrate +-10 —'13 



+ 1*07 -*89 +1*39 -1*22 



