What is part 3 of poem Vapor Trail Reflected in the Frog Pond about?

In the third part of the poem "Vapor Trail Reflected in the Frog Pond", the poet Gary Snyder reflects on the cyclical nature of time and existence. He acknowledges that the frog pond, which he had once observed as a child, is no longer the same as he had then remembered it. He contemplates how nature has undergone changes, and how his own life and memories are also subject to transformation and decay. The poet realizes that the vapor trails left by airplanes in the sky are fleeting, just as his own life and the moments he has cherished will eventually fade away. He accepts the impermanence of everything, finding beauty and wisdom in the constant cycle of change and renewal.