1878.] 
On Residual Phenomena. 
27 
precautions he has taken to eliminate all sources of error, 
will be unable to conceive of any further improvements 
adequate to convert the fractions here given into whole 
numbers. 
But let us re-consider the atomic weights of the nine 
elements above quoted. In three cases only do we find the 
fraction extending to the first decimal place ; in four others 
it commences with the second decimal, being always less 
than o'Oj ; whilst in the remaining two elements the dif- 
ference between the atomic weight experimentally determined 
and the calculated figure is confined to the third decimal. 
If we suppose, with Dumas, that the common divisor may 
be 0'5, we have the following differences between the experi- 
mental and the hypothetical nnmbers : — 
Oxygen 
0*040 
Silver 
0*100 
Nitrogen 
0*009 
Bromine 
0*250 
Chlorine 
0*132 
Iodine 
0*033 
Lithium 
0*004 
Potassium 
0*040 
Sodium 
0*020 
Or, as Prof. Stas himself expresses the matter, “ The 
greater part of carefully-determined weights come so near 
to calculated ciphers that it has been necessary to have 
recourse to all the arts and refinements of analysis to prove 
that they are not absolutely exadt.” But if we take the 
weights as given by earlier authorities, and, it may be ad- 
mitted, determined, if not with less skill, yet without the 
aid of the most recent appliances, we find the difference 
between the experimental result and the calculated number 
in many cases even greater than those shown by the re- 
searches of Prof. Stas. 
Thus the older numbers are — - 
Oxygen 
16*0 
Silver 
108*1 
Nitrogen 
14*0 
Bromine 
7 8 '4 
Chlorine 
35‘4 
Iodine 
126*0 
Lithium 
6*4 
Potassium 
39*2 
Sodium 
23*2 
