1864.] Optine on the Proportional Numbers of the Elements. 
647 
atomic weights, may be brought into association with one another, 
thus :— 
4h 
Cr 
x Ag 
Zn 65 Cd 
23 » 
24 ” ” 
ai Sn 
Zio U 
As 175 Sb 
28 35 Pr 
31 99 ” 
3 Se 79°5 Te 
Br 80 I 
35:5 5 FA 
39 Rb 85 Cs 
9 AY 
40 Sr 87:5 Ba 
Zr 89°5 Ta 
Ce 92 Pe 
Mo 96 * 
50 ” 9 
52°53 7 
108 | Au 196-5 
112 | He 200 
Tl 203 
Pb 207 
118 : 
120 ‘3 
122 | Bi 210 
129 s 
127 - 
133 . 
137 3 
13 e 
138 : 
Th 231°5 
» 
The parallelism between the monatomic and diatomic alkaline 
groups, 18 shown still more strikingly below :— 
Dif, 1. 
23 
24 
39 
40 
Dif. 2. 
DE 63 
Zn 65 
Rb 85 
Sr Sub 
Dif, 4. Dif. 4. 
g 108 Au 196°5 
Cd 112 | Hg 200 
» Tl 203 
» Pb 207 
Cs 133 rs 
Ba 137 
Seeing the large number of instances in which the atomic weights 
of proximate elements differ from one another by 48, or 44, or 40, or 
16, we cannot help looking wistfully at the number 4, as embodying 
somehow or other the unit of a common difference, especially when 
we find in addition that several pairs of strictly analogous elements 
differ in atomic weight by this same number, as shown below :— 
fl Te Ae] 
ed 
52°5 = Be 
dd = 4 
59 = 495 
92 = 4 
