Conversation so far:
When did William Cullen go to the University of Edinburgh?
In 1755 William Cullen become Professor of Chemistry and Medicine at the University of Edinburgh.
Why did William Cullen go to the University of Edinburgh?
William Cullen was enticed by Lord Kames to become Professor of Chemistry and Medicine at the University of Edinburgh.

Question: How long did he teach there?
Self-contained rewrite: How long did William Cullen teach at the University of Edinburgh?