Pope has borrowed the conceit from Donne in An Essay on Criticism, ll. 54-9:
As on the land while here the ocean gains,
In other parts it leaves wide sandy plains;
Thus in the soul while memory prevails,
The solid power of understanding fails;
Where beams of warm imagination play,
The memory's soft figures melt away.
l. 34. For, graves our trophies are, and both deaths dust. The modern printing of this as given in the Grolier Club edition makes this line clearer—'both Deaths' dust.' 'Graves are our trophies, their dust is not our dust but the dust of the elder and the younger death, i.e. sin and the physical or carnal death which sin brought in its train.' Chambers's 'death's dust' means, I suppose, the same thing, but one can hardly speak of 'both death'.
Page 281, ll. 57-8.
this forward heresie,