Digby
Yes Really!
See page 74. Letter 552, Napoleon to Clarke Sept. 7, 1809.
The Confidential Correspondence of Napoleon Bonaparte with His Brother Joseph Volume II.
http://books.google.ca/books?id=F1MRAAAAYAAJ&printsec=frontcover&dq=
See also pages 123-124. Letter 619, Napoleon to Berthier, May 29, 1810. Issuing similar orders to Massena regarding September and when heats were over.
Good hunting.
Ron