The 'A. S. Hewitt', who was unable to attend the dinner in honour of Whistler at the Criterion in 1889, may have been Abraham (Abram) Stevens Hewitt, manufacturer and founder of 'The Cooper Union'.
It is not known if he was in London in 1889, but it is likely that he knew Whistler at that time, in the late 1890s.
Alternatively, the Hewitt known to Whistler could have been Abram S. Hewitt, lawyer, the Mayor of New York, and Chairman of the Carnegie Institute.
www.picturehistory.com (accessed 2005).