It is the evening before Dorian's thirty-eighth birthday, and he has dined with Lord Henry.
The extended simile in the passage is: As when a circling wall the builder forms, Of strength defensive against wind and storms, Compacted stones the thickening work compose, and round him wide the rising structure grows.
A simile is a figure of speech that compares one thing from another thing of a different kind. It adds meaning to the text because it emphasizes the:
a. Strength of the wall - which is likened to being a barrier that can be used as protection from wind and storms.
b. Size of the structure - which was built with hours of hard work and construction materials that can withstand such great forces of war.
It's the last one. we know this because it talks about how even with the smart hands of a scientist, the plan is not completely foolproof, or safe
