The Great Jigsaw  Experiment by Arsinoë

The first letter of each answer is to be entered at its corresponding number in the grid, the last letter at the asterisk within the same piece (as delineated by the thicker bars), and the remaining letters scrambled. The correctly completed grid (reading from top to bottom and left to right) will reveal an abridged quotation concerning the impossibility of incorruptibility. Individual words in the quotation are indicated by the alternating grey and white shading in the grid.

1 Fashionable fellow to contemplate switching hands (5)
2 Object subsumed by request to stop pouring bleach (6)
3 Profundity of upright pedagogue somewhat taken aback (5)
4 Floating escorts sent primarily across turbulent river, regardless of velocity (7)
5 Luxurious benefit enunciated by the intoxicated? (5)
6 Scarcely frayed edges of lavish Indian tapestry (6)
7 Hoover’s boys captivated by competent contrivance (7)
8 Shakespeare made him sign a potentially bloody contract (7)
9 Nothing obtained with loss of capital (5)
10 Foolish ones return if not left out, for example (5)
11 British agents concealed early pro golfer (5)
12 Buttonhole carnation chiefly wreathed by untidy ascot (6)
13 Urged initially with gravity in hibernal race, descended at last (5)
14 Piano and organ have excellent pitch (6)
15 Hint nearly comprehended by criminal syndicate on a rampage (7)
16 Something stale has her in a ferment (6)
17 Doctor’s clean instrument ultimately without a speck? (6)
18 Reportedly divine Arabian lateen-rigged vessels (5)
19 Ocean passage where Dr. Spooner finds diminutive whale (6)
20 Almost notice incoherent keynote (5)
21 They provide structural integrity for bombers? (5)
22 Aggregate time given by off-key alto (5)
23 Donald’s nephew’s Lewis’ helicopters (5)
24 Mole displaces sediment at first in healthy pile (5)
25 Boost flagging pair during practice (7)
26 Principally fabrics employed lining tables, sportingly (5)
27 Speaking of royal nickname is perilous (5)
28 To expose weakness, try to interrupt rap expert’s witty remark (5)
29 Rotated forty-five degrees, that which binds is laced together (5)
30 Historically, he declared halfheartedly “Take your base” (7)