In 1825, he became professor of mathematics and natural philosophy at Yale. He published an elaborate theory of hail-stones in 1830, which caused much discussion, but finally received the general approbation of meteorologists. The shower of shooting stars that fell in November 1833 attracted his attention, and he studied their history and behavior until he was able satisfactorily to demonstrate their cosmical origin. Olmsted appears to have been the earliest person to use the word radiator to mean a heating appliance in a patent of 1834 when he wrote that it was "a peculiar kind of apparatus, which I call a radiator". Olmsted and his associate, Elias Loomis, were in 1835 the first American investigators to observe the Halley's Comet.