Note 45 — SPRING:
Reading edition
It is evident from the mention of the "golden sands" of Pactolus, and the "amber" of the poplars in connection with the Thames, that he had in view Denham's description in Cooper's Hill:
Though with those streams he no resemblance hold, Whose foam is amber, and their gravel gold.—Wakefield.
The sisters of Phæton, according to the classical fable, were, upon the death of their brother, turned into poplars on the banks of the Po, and the tears which dropt from these trees were said to be converted into amber.