The author's excellent 'powers of observation' [=ability to notice and pay close attention to things] are evident in the book's detailed descriptions.
The plants seem to have recovered from the disease, but they are still 'under observation'. [=someone is watching them carefully]
They're keeping him at the hospital 'for observation' [=so that doctors can watch him carefully] for another few days.
(..) Remember thee? Yea, from the tables of my memory I'll wipe away all trivial fond records All saws of books, all forms, all pressures past, that youth and observation copied there And thy commandment all alone shall live within the book and volume of my brain... ...unmixed with baser matter. (..)2015 Hamlet