I haven't read much of Adams; but my favorite Adams oration is online, at Project Gutenberg: "The Jubilee of the Constitution, delivered at New York, April 30, 1839, before the New York Historical Society." The speech is an argument that the Constitution improved upon the Articles of Confederation by returning the principles of the Declaration of Independence. My favorite part:
And thus was consummated the work commenced by the Declaration of Independence--a work in which the people of the North American Union, acting under the deepest sense of responsibility to the Supreme Ruler of the universe, had achieved the most transcendent act of power that social man in his mortal condition can perform--even that of dissolving the ties of allegiance by which he is bound to his country; of renouncing that country itself; of demolishing its government; of instituting another government; and of making for himself another country in its stead.
And on that day, of which you now commemorate the fiftieth anniversary--on that thirtieth day of April, 1789--was this mighty revolution, not only in the affairs of our own country, but in the principles of government over civilized man, accomplished.
The Revolution itself was a work of thirteen years--and had never been completed until that day. The Declaration of Independence and the Constitution of the United States are parts of one consistent whole, founded upon one and the same theory of government, then new in practice, though not as a theory, for it had been working itself into the mind of man for many ages, and had been especially expounded in the writings of Locke, though it had never before been adopted by a great nation in practice.
I don't agree with all of Adams's argument (I don't have quite the animus against the Articles of Confederation that he did), but I think he was on to something.
You can also find Adams's State of the Union addresses. I looked over them when composing this post, and was rather saddened by the thought that they show so vividly a decline in the governance of our great nation: compare the propagandistic, self-aggrandizing pap of modern addresses with the substantive addresses -- sometimes short, but almost always conveying crucial points -- of early Presidents like Adams. For that matter, compare recent Presidents to the Presidents of the middle of the twentieth century. To some extent it's a matter of subjective judgment, but it seems to me that, while there were already clear signs of decline, there begins to be sharp decline in quality of thought with Johnson; in particular, a massively increased tendency to tell us less about the state of the Union and more about why we should believe that the President is brilliant. Looking at various online summaries of the history of the addresses, I wonder if the reason has to do with television. Truman's 1947 State of the Union was the first to be televised. And perhaps it has some effect on the speeches of Truman, Eisenhower, and Kennedy. But Johnson must have been very aware of the political value of television, since he's the one who moved the State of the Union to prime time; and comparing his addresses to those of Truman, Eisenhower, and Kennedy is a bit jarring. Starting with Johnson the advertisements and excuses, and endless egoistic self-parading, seem to begin in earnest. And it doesn't really get better at any point, although to be fair, Reagan at least has the decency to make the excuses and advertisements less obvious - he's politicking rather than giving us the state of the Union, but at least he sometimes manages to sound like he's telling us about the state of the Union. Clinton and the Bushes are all shameless, although Bush Sr.'s first address starts out on the right note. Of course, it seems to have been Reagan who started that nasty, horrible habit of actually having in the address a sentence saying something like "The State of the Union is strong" -- the most uninformative do-nothing politically-smarmy sentence you can find in any State of the Union address; and it has come up often. When Wilson re-instated the long-dead practice of delivering the State of the Union address in person, the practice having been killed by Jefferson's refusal to act like a monarch, he was attacked by members both within and without his party for trying to imitate the silly pompousness and cavalcades of despots. Perhaps it's time we started saying the same.
(A good essay on the problem of the televised addresses here.)