What's the meaning of this term “November’s gray dissolution”
He ranged the summer woods now, green with gloom if anything actually dimmer than they had been in November’s gray dissolution.
What's the meaning of this term “November’s gray dissolution”

Question

What's the meaning of this term “November’s gray dissolution”
He ranged the summer woods now, green with gloom if anything actually dimmer than they had been in November’s gray dissolution. 
What's the meaning of this term “November’s gray dissolution”

Answer

Dissolution can be used in a number of different ways:
https://www.merriam-webster.com/dictionary/dissolution

I think that, in this case, the writer means: the end of November, or the closing out of November (the last few days). They're talking about it getting darker, more sombre, the days are shortening and the weather is getting worse - cloudy, rainy, etc (grey).

I think the writer is deliberately using two meanings. The ending of November/autumn, and dissolving into winter.