Alexander von Humboldt Autograph

Autograph letter signed, one page - also addressed to the reverse of the conjoined sheet, 4 x 5 inch, in French, to Joseph-Philippe-François Deleuze (1753-1835, 18th-19th-century French naturalist) - concerning an advice about a philosophical text and an appointment, written and signed in dark ink "Humboldt", attractively mounted (removable) for fine display with a picture of Alexander von Humboldt (altogether 11,75 x 8,25 inch), with mild letter folds, mounting remnants to the upper right corner, and scattered mild signs of wear - in fine condition.

In parts:
"Lisez, mon respectable ami, ce petit écrit très philosophique, lisez surtout les dernières pages. J`aurai bien besoin ce matin de Vos aimables conseils pour une seule heure: Il me serait le plus commode de me présenter chez Vous avant Votre diner à quatre et demie (4h 1/2), cela Vous serait-il agréable ? Dans le cas contraire daignez me fixer toute autre heure depuis 10 h à 5 h. Mille tendres hommages [...]
  Humboldt"

Translated:
"Read, my respectable friend, this short, very philosophical piece, especially the last pages. I would greatly appreciate your kind advice for just one hour this morning: It would be most convenient for me to come to your house before your dinner at 4:30. Would that be agreeable to you? If not, please allow me any other time between 10:00 and 5:00. With warmest regards, [...]
   Humboldt"