Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Passage: Barton Stone Alexander (September 4, 1819 December 15, 1878) was a Union Army lieutenant colonel, engineer regiment commander and chief engineer for the defenses of Washington during the American Civil War. In recognition of his service, in 1866, he was appointed to the brevet rank of brigadier general in the regular army, to rank from March 13, 1865. He was a graduate of the U.S. Military Academy at West Point and served in the United States Army's Corps of Topographical Engineers, which at times was both a part of and separate from the United States Army Corps of Engineers. After graduating from West Point as a second lieutenant in the Class of 1842, he served in the MexicanAmerican War, building fortifications to protect American supply lines in the advance on Mexico City. After the end of the war, he was stationed in Washington, D.C., where he served as architect for the Scott Building and Quarters Buildings at the U.S. Soldiers' Home and took over the completion of the Smithsonian Institution Building after dissatisfaction with the pace of the first architect caused him to be dismissed.
Link Information: none Question: What ranks come before the one Barton graduated with in 1842?
A:
Answer: none