This is Alexander Turnbull (14 September 1868 – 28 June 1918) at the age of 23.
If you want to know more about him read Jim Traue's short biography
or tackle E.H.McCormick's full scale biography.
On Turnbull's death, his bequest to the National Library led to a research library established in his name. His gift included over 55,000 books.
Turnbull is sometimes described as a dandy.