484 Prof. Odling on the Natural Groupings 



fL = 6-5 68-5 -_„ 



IstJNa = 23-0 -^=22-8 mean. 



[k = 390 



Sum 68'5 Mean diflference = 16. 



rMg= 12-16 100-36 „- .. 



2nd.^ Zn = 32-50 —3— =33-45 mean. 



[Cd = 55-75 



Sum 100-36 Mean difFerence =20. 



fCa = 20 132-3 ,, , 



3i-d.^ Sr = 43-8 -3- = 44-l mean. 



l^Ba = 68-5 



Sum 132-3 Mean difference =24. 



We perceive that the three sums^ the three means, and the 

 three differences are all in proportional sequence : — 



Sums. Means. Differences. 



68-5 22-8 16 



100-36 33-45 20 



132-3 44-1 24 



3 301-16 3 100-35 3 60 



100-38 33-45 20 



Moreover, it is observable that while the atomic weight of cal- 

 cium is the atomic weight of the first member of the third group, 

 the atomic weight of strontium is the sum of the atomic weights 

 of the first two members of the second group, and the atomic 

 weight of barium is the sum of the atomic weights of all three 

 members of the first group. 



Many other relations at once strike the eye. Thus the atomic 

 weight of lithium is one-half that of magnesium, and one-third 

 that of calcium. Sodium -\- zinc = cadmium; calcium -\- mag- 

 nesium = zinc, &c. The sum of the means = the mean of the 

 sums, and many other necessary consequences. 



Group VIII. Glucinum, Yttrium, Thorium, 



Our acquaintance with these elements is insufficient to war- 

 rant our laying much stress upon the existence of the group. 

 At the same time the three metals seem to present many ana- 

 logies. Yttrium is probably associated with erbium and terbium 

 by the relation of equality. The sequence of atomic weights is 

 very exact : — 



Gl = 4-7 96-3 „„, 



Y _ 00 — K— = 32-1 mean. 



Th = 59-6 



Sum 96-3 Mean difference =28. 



