Despite his setbacks, he set forth on a new expedition in 1854, this time to the Malay Archipelago which makes up modern day Indonesia and the Philippines. It was here that he solidified his ideas about how species change over time. He sent his work to Darwin for review in 1858. He asked Darwin to forward his work to Charles Lyell, if Darwin found his ideas "sufficiently novel and interesting." The Linnean Society published excerpts from both Darwin and Wallace in August 1858, which was the first publication of either scientist's work on the subject.
Beccaloni, G. W. 2013. Alfred Russel Wallace and Natural Selection: the Real Story. <http://downloads.bbc.co.uk/tv/junglehero/alfred-wallace-biography.pdf