The air is of late cooler and clearer, autumnal.

September 2. 

P. M. — To Ledum Swamp. 

The pontederia leaves are now decidedly brown or brownish, and this may be the effect of frost, since we have had some considerable in low places. Perhaps they occupy particularly cold places. 

The farmer is obliged to hide his melon-patch in the midst of his corn or potatoes, far away. I sometimes stumble on it as I am going across lots. I see one to day where the watermelons are intermixed with carrots in a carrot-bed, and so concealed by the general resemblance of leaf, etc., at a little distance. 

Going along Clamshell Hill, I look over the meadows. Now, after the first rain raising the river, the first assault on the summer's sluggishness, the air is of late cooler and clearer, autumnal, and the meadows and low grounds, which, of course, have been shorn, acquire a fresh yellowish green as in the spring. This is another phase of the second spring, of which the peeping of hylas by and by is another. 

I once did some surveying for a man who remarked, but not till the job was done, that he did not know when he should pay me. I did not pay much heed to this, though it was unusual, supposing that he meant to pay me some time or other. But after a while he sent to me a quart of red huckleberries, and this I thought was ominous and he distinguished me altogether too much by this gift, since I was not his particular friend. I saw it was the first installment, which would go a great way toward being the last. In course of years he paid a part of the debt in money, and that is the last I have heard of it. 

The sarothra grows thickly, and is now abundantly in bloom, on denuded places, i.e., where the sod and more or less soil has been removed, by sandy roadsides. 

At Ledum Swamp the frosts have now touched the Polygonum Careyi pretty extensively, the leaves and stem, leaving the red spikes; also some erechthites and poke and the tenderest high blueberry shoots, their tips (from where the bushes were cut down). But the Woodwardia Virginica is not touched. (Vide back, August 23d.) 

Poke berries begin at Corner Spring.

H. D. Thoreau, Journal, September 2, 1859

Now, after the first rain raising the river, the first assault on the summer's sluggishness, the air is of late cooler and clearer, autumnal. See September 2, 1854 ("Bathe at Hubbard’s. The water is surprisingly cold on account of the cool weather and rain, but especially since the rain of yesterday morning. It is a very important and remarkable autumnal change. It will not be warm again probably"); September 3, 1860 ("Here is a beautiful, and perhaps first decidedly autumnal, day, -- a, cloudless sky, a clear air, with, maybe, veins of coolness”); September 11, 1853 ("Cool weather. Sit with windows shut, and many by fires. . . .The air has got an autumnal coolness which it will not get rid of again.")

The meadows acquire a fresh yellowish green as in the spring. This is another phase of the second spring, of which the peeping of hylas by and by is another. See  August 4, 1853("The low fields which have been mown now look very green again in consequence of the rain, as if it were a second spring."); August 7, 1852 ("At this season we have gentle rain-storms, making the aftermath green . . . as if it were a second spring."); September 14, 1852 ("The grass is very green after the rains, like a second spring,"); October 23, 1853 ("Many phenomena re mind me that now is to some extent a second spring, — not only the new-springing and blossoming of flowers, but the peeping of the hylodes for some time, and the faint warbling of their spring notes by many birds.")

But after a while he sent to me a quart of red huckleberries, and this I thought was ominous.See January 25, 1858 ("I am amused to see what airs men take upon themselves when they have money to pay me.")

The sarothra grows thickly, and is now abundantly in bloom. See August 30, 1856 ("The sarothra is now apparently in prime on the Great Fields, and comes near being open now, at 3 p. m. Bruised, it has the fragrance of sorrel and lemon, rather pungent or stinging, like a bee.”); August 12, 1856 (“The sarothra — as well as small hypericums generally — has a lemon scent.”)

The Woodwardia Virginica is not touched. See September 6, 1858 ("At Ledum Pool edge, I find the Woodwardia Virginica fern, its fruit mostly turned deep reddish-brown")