増す: stronger wind and enhanced beauty
Identify the strength of the wind and the beauty of a vessel as what increases, preserving the past change and the polishing condition.
Wind becoming stronger as night falls
日が暮れるにつれて風の強さが増した。 reports the wind growing stronger as night fell. 増す, read ます, takes 風の強さ as the increasing property, with 増した reporting a past change.
日が暮れるにつれて connects the falling night with the strengthening wind. No exact wind speed or increase amount is supplied, but the change in strength is stated.
Beauty under a polishing condition
丁寧に磨けば器の美しさが増す。 says that careful polishing will enhance the vessel's beauty. 器の美しさ is the property enhanced, and 丁寧に磨けば supplies the condition.
Do not turn this conditional into a past report that the vessel was already polished. Enhanced beauty does not mean that the number of vessels increased or that another vessel was bought.
Identify what increases
The subjects are wind strength and a vessel's beauty. Identifying them prevents treating the examples as an increase in object count or a fixed percentage.
The first reports stronger wind as an actual past change. The second relates enhanced beauty to polishing. Preserve the object difference alongside the past-versus-conditional distinction.
Does 器の美しさが増す mean that the number of vessels increases?
Show the answer and why
No. It concerns beauty enhanced through careful polishing. The increasing property is not the vessel count, and completed polishing is not supplied.