Which preposition to use with marchand

at Occurrences 1%

He also informs me that Marchand at the Pic du Midi Observatory was unable to obtain lines of aqueous vapour in the spectrum of Mars; and that in 1905, Slipher, at Mr. Lowell's observatory, was unable to detect any indications of aqueous vapour in the spectrum of Mars.

for Occurrences 1%

But I shall sing those songs to Marchand for himfor all they're worth.

from Occurrences 1%

Delcassé was finally able to quiet the French people, to recall Marchand from Fashoda and to persuade France to refuse the offer of German friendship.

Which preposition to use with  marchand