Explanation: And here let those... And hands innumerable, scare perform. (Lines 692-699)

Explanation:
"And here let those
Who boast in mortal things, and wondering tell
Of Babel, and the works of Memphian kings,
Learn how their greatest monuments of fame,
And strength, and art, are easily outdone
By spirits reprobate, and in an hour
What in an age they, with incessant toil
And hands innumerable, scare perform.”
(Lines 692-699)

Answer: These lines, set for explanation, occur in 'Paradise Lost' Book-I the most notable epic in English language by John Milton. The poet, here, gives a classic description of the extraordinary powers of the fallen angels in building the magnificent Pandemonium.

The poet says that those who speak with pride and a sense of glory about men's achievement in architecture by referring to the huge buildings (temples and pyramids) of ancient Egypt, would do well to learn that the most magnificent achievements of men are nothing in comparison to the skill that the angels displayed in building the Pandemonium. The proudest achievement of men of ancient Babylon and Egypt, which were completed after years of incessant toil by men, possessing extra-ordinary skill, are easily excelled in grandeur and magnificence by the resources of the fallen angels. The fallen angels are capable of building finer and more magnificent things than the finest building constructed by the kings. of Egypt and Babylonia.

The reference to the works of Memphian kings is based on the account given by Greek writers. The following comment by Rajan supplies us with the necessary information in this respect, "According to Diodorus Siculus and Pliny 3,50,000 men were employed for about twenty years in building the Great Pyramid. Pliny considers the Pyramids to be "idle and frivolous pieces of ostentation', and adds that accident has 'with very considerable justice, consigned to oblivion the names of those who erected such stupendous memorials to their vanity'. Sandys, similarly, describes the pyramids as barbarous monuments of prodigality and vain glory.' Pandemonium is built without the labour needed for the pyramids but it is subject to a similar valuation. Babel (694), is sometimes explained as meaning 'Babylon but the reference is probably to the tower of Babel."