Hon. Norman Wingfield,
Secretary of the Treasury.

Sir:

Hon. Rupert Gresham,
Mayor of New York.

Sir:

Presidents and Professors of Colleges and Universities are generally
addressed as _Sir_ or _Dear Sir_.

Professor Ferguson Jenks,
President of .......... University.

Sir: or Dear Sir:

Presidents of Societies and Associations are treated as business men and
addressed as _Sir_ or _Dear Sir_.

Mr. Joseph Banks,
President of the Night Owls.

Dear Sir: or Sir:

Doctors of Medicine are addressed as _Sir: My dear Sir: Dear Sir:_
and more familiarly My dear Dr: or Dear Dr: as