Yeah, there is a good reason people don't talk like that any more.
The year that is drawing towards its close (1), has been filled with the blessings of fruitful fields and healthful skies (2).
To these bounties (3), which are so constantly enjoyed (4) that we are prone to forget the source from which they come (5), others have been added (6), which are of so extraordinary a nature (7), that they cannot fail (8) to penetrate and soften even the heart (9) which is habitually insensible to the ever watchful providence of Almighty God (10).
- It is November 28, 1861, so the year is almost over. Let's talk about 1861.
- We have been having good weather, so the harvest has been good.
- In addition to the good weather and the good harvest
- Good weather and good harvest are common
- (4) is so common, we don't even think about where they come from (God)
- Other good stuff has happened
- The good stuff from (6) is unusual.
- Because the unusual good is unusual, it is going to have an effect
- The effect is changing the minds of people like Bob
- People like Bob usually don't think about God.
Item (7) is really your answer. The nature (the innate characteristics) of some of the events of 1861 was extraordinary.
I still don't know what Lincoln was talking about. 1861 was a terrible year in American history, arguably the worst year in American history. A third of the country had decided that keeping slavery was more important than the country itself. The Union was disintegrating into fratricidal war. Thousands of young men were slaughtering each other every day. The First Battle of Bull Run, the Battle of Corrick's Ford, the Battle of Wilson's Creek, the invasion of Kentucky, Santa Rosa Island, Ball's Bluff, Belmont, Round Mountain: so far from softening the hearts of the irreligious, the "bounty" of 1861 might make the pious question the existence of God.