and have it once for ever at rest. Say to him that profiting by his suggestion and advice I, — K.H., will appear to Eglington [sic] in propria persona as in actu at sea, between the 21 and 22 of this month; and that, if successful in bringing the rebel who denies the "Brothers" to his senses, Mrs. Gordon and consort — will be notified of the fact immediately. That's all. We have, waited on purpose to produce our experiment until his departure, and now — WE MEAN TO ACT.
"in propria persona" means to represent oneself in court without assistance of an attorney, from the Latin for "in ones own proper person."
"in actu" is a Latin phrase meaning "in the very act"