By deputation

by delegated authority; as substitute; through the medium of a deputy.

See also: Deputation

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
The danger of delay obliges the consenting provinces to furnish their quotas, without waiting for the others; and then to obtain reimbursement from the others, by deputations, which are frequent, or otherwise, as they can.
The petitioner claimed that the post of special secretary couldn't be filled by deputation.