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of Edinburgh^ Session 1863 - 64 . 
5. Bromomaleic and isobromomaleic acids. 
6. The two hibromosuccinic acids. 
7. The two varieties of malic acid. 
8. The two varieties of aspartic acid. 
9. Two of the varieties of tartaric acid. 
10. Two of the dehydrogenates of pyrotartaric acid. 
11. Two of the three bibromopyrotartaric acids. 
The following are shown to be probably metameric , — - 
1. The compounds of ethylene and of ethylidene. 
2. The alcohols' proper and the hydrates of the olefines. 
3. Lactic and paralactic acids. 
The next point considered is the influence which the existence 
of such pairs of substances has on the theory of atomicity, and 
particularly on the question whether all the equivalents of a multe- 
quivalent atom are of the same chemical nature. 
The consideration of absolutely isomeric bodies leads to the con- 
clusion that there is a difference among the equivalents of the same 
atom, and that this difference is not entirely due to the structure 
of the molecule of which the atom forms a part. It is not, how"- 
ever, possible as yet to apply this principle to the explanation of 
particular cases. 
The remarks of Professor Kekule on the isomerism of the dehydro- 
genates of succinic and of pyrotartaric acids, and those of Professor 
Butlerow on the isomerism of methyl gas and hydride of ethyl, are 
then considered in detail, and Butlerow’s hypothesis compared with 
the views of Kolbe as to the chemical nature of carbon. 
2 H 
\^OL. V. 
