Complex sentence: In 1810, he was granted a two-year furlough to command John Jacob Astor's sailing bark "Tonquin" in the Astor Expedition for the Pacific Fur Company to the Pacific Northwest to establish a fur trading post.
Split into simpler sentences: In 1810, he was granted a two-year furlough to command the Pacific Fur Company's sailing bark, the "Tonquin", owned by John Jacob Astor. The "Tonquin" was to sail to the Pacific Northwest to establish a fur trading post.