A different order, equally characteristic, is discovered in Wallace’s writings, and it is to be noted that while Darwin devoted himself entirely to scientific subjects, Wallace diverged at intervals from natural science to what may be termed the scientific consideration of social conditions, in addition to his researches into spiritualistic phenomena.

The many enticing interests arising out of the classifying of his birds and insects led Wallace to the conclusion that it would be best to postpone the writing of his book on the Malay Archipelago until he could embody in it the more generally important results derived from the detailed study of certain portions of his collections.  Thus it was not until seven years later (1869) that this complete sketch of his travels “from the point of view of the philosophic naturalist” appeared.

Between 1862 and 1867 he wrote a number of articles which were published in various journals and magazines, and he read some important papers before the Linnean, Entomological, and other learned Societies.  These included several on physical and zoological geography; six on questions of anthropology; and five or six dealing with special applications of Natural Selection.  As these papers “discussed matters of considerable interest and novelty,” such a summary of them may be given as will serve to indicate their value to natural science.

The first of them, read before the Zoological Society in January, 1863, gave some detailed information about his collection of birds brought from Buru.  In this he showed that the island was originally one of the Moluccan group, as every bird found there which was not widely distributed was either identical with or closely allied to Moluccan species, while none had special affinities with Celebes.  It was clear, then, that this island formed the most westerly outlier of the Moluccan group.

The next paper of importance, read before the same Society in November (1863), was on the birds of the chain of islands extending from Lombok to the great island of Timor.  This included a list of 186 species of birds, of which twenty-nine were altogether new.  A special feature of the paper was that it enabled him to mark out precisely the boundary line between the Indian and Australian zoological regions, and to trace the derivation of the rather peculiar fauna of these islands, partly from Australia and partly from the Moluccas, but with a strong recent migration of Javanese species due to the very narrow straits separating most of the islands from each other.  In “My Life” some interesting tables are given to illustrate how the two streams of immigration entered these islands, and further that “as its geological structure shows ...  Timor is the older island and received immigrants from Australia at a period when, probably, Lombok and Flores had not come into existence or were unhabitable....  We can,” he says, “feel confident that Timor has not been connected with Australia, because it has none of the peculiar Australian mammalia, and also because many of the commonest and most widespread groups of Australian birds are entirely wanting."[2]