General St.Clair was appointed to the command of an expedition to Canada, and he invited Hume, at a week's notice, to be his secretary; to which office that of judge advocate was afterwards added.
Hume writes to a friend: "The office is very genteel, 10_s_.

a day, perquisites, and no expenses;" and, to another, he speculates on the chance of procuring a company in an American regiment.

"But this I build not on, nor indeed am I very fond of it," he adds; and this was fortunate, for the expedition, after dawdling away the summer in port, was suddenly diverted to an attack on L'Orient, where it achieved a huge failure and returned ignominiously to England.
A letter to Henry Home, written when this unlucky expedition was recalled, shows that Hume had already seriously turned his attention to history.

Referring to an invitation to go over to Flanders with the General, he says: "Had I any fortune which would give me a prospect of leisure and opportunity to prosecute my _historical projects_, nothing could be more useful to me, and I should pick up more literary knowledge in one campaign by being in the General's family, and being introduced frequently to the Duke's, than most officers could do after many years' service.

But to what can all this serve?
I am a philosopher, and so I suppose must continue." But this vaticination was shortly to prove erroneous.