between the Atomic Weights. 395 
with chlorine ; and since, not only from its analogies, but also 
from its atomic weight, it appears to be the nucleus in all the 
first three series, I have placed it at the head of each. It ma 
be mentioned here, that in all cases the fact that the atomic 
weight of an element is included in the general formula of a series, 
isan argument for classifying it in that series, if the relation between 
the atomie weights pointed out in this memoir is admitted to be 
a law of nature; but as I wish to show that the relation is not 
that of a mere accidental group of numbers, but is connected 
with the most fundamental properties of the elements, and has, 
therefore, the claims of a law, I have endeavored to show the 
correctness of the classification which conforms to the law, and, 
indeed, in fact suggested the law on other grounds. 
The atomic weights of the numbers of the Nine Series, as de- 
termined by experiment, present greater deviations from the nu- 
merical law already explained, than are to be found in any of the 
others. The weights which would exactly conform to the gene- 
ral formula 8+79 are given in the column of the table headed 
Theoretical, while in the next column at the right are given the 
weights of experiment. These for the most part (in this as well 
as in the other series), have been taken from the table of Atomic 
Weights given in the last yonirt of Liebig and Kopp, Jahres- 
bericht for 1852, which was supposed to i the cae and most 
accurate results. In the few cases in which the numbers have 
hot been taken from this table, the initial letter of thd name of 
the observer has been annexed. It will be seen, on comparing 
the two columns that the greatest deviation from the law is in: 
the case of fluorine, if we consider the care which was taken both 
by Berzelius and Louyet i in the determination of the atomic weight 
of this element. It may, however, be remarked, that, as the pro- 
cesses used by both experimenters were essentially identical, any 
lidden constant source of error would produce the same effect 
on both results; so that the atomic weight of fluorine cannot be 
Tegarded as yet absolutely fixed. ih ti it is not possi- 
le that so great a difference between the true and observed 
Weights as two units could have escaped aenssied in the number- 
less analyses which have been made, by the most experienced 
chemists, of the fluorine compounds. It must, therefore, be ad- 
mitted, and not only in the case of fluorine, but also in other in- 
stances, that there are deviations 8 the law ; but these devia- 
tions are not greater than those from similar numerical laws in 
astronomy atid other sciences, and indeed, judging from the anal- 
ogy of Fi sciences, they ought to be expected. 
who are not familiar with the amounts of probable error 
in the de determmation of the different atomic weights would judge, 
on comparing together the columns of theoretical and obser 
Values, that the deviations from the law were much greater than 
