A little further down...
The personal independence of the president is secured by that clause, which provides that he shall receive a compensation at stated periods, which shall not be diminished during his continuance in office. To guard against avarice, corruption, and venality, it is also provided, that it shall not be encreased during the same period, nor shall he receive within that period any other emolument from the United States, or either of them. His salary, as now fixed by law, seems to be fully adequate, though far below the income of many private persons in England, and even in America. The political independence of the president of the United States, so far as it is necessary to the preservation, protection, and defence of the constitution, is secured, not only by the limitations and restrictions which the constitution imposes upon the legislative powers of congress, but by a qualified negative on all their proceedings, as has been already mentioned elsewhere.
(emphasis in the opriginal)