“Other religions, indeed, are quite as full of miracles; the heathen boasts of many, so does the Turk; no religion is without them, and this it is which also makes the Christian miracles so doubtful, and provokes us to ask: "Did the events really happen? Were the attendant circumstances such as are stated? Did they come to pass naturally, or by craft, or by chance?"… those who would build Christianity upon miracles give it nothing firm, deep or substantial for a foundation.”

Source: Fragments from Reimarus: Consisting of Brief Critical Remarks on the Object of Jesus and His Disciples as Seen in the New Testament, p. 69

Letter to Thomas Jefferson (3 December 1813), published in Adams-Jefferson Letters: The Complete Correspondence Between Thomas Jefferson and Abigail and John Adams http://books.google.com/books?vid=ISBN0807842303&id=SzSWYPOz6M8C&pg=PP1&lpg=PP1&ots=kTAZL3ImRq&dq=%22Adams-Jefferson+letters%22&sig=tVGzBe0XVhXaF2p0FQLGy4GK6bk#PRA2-PR17,M1 (UNC Press, 1988), p. 404
1810s

Legislative Assembly, February 9, 1865
Context: Miracles would cease to be miracles if they were events of everyday occurrence; the very nature of wonders requires that they should be rare; and this is a miraculous and wonderful circumstance, that men at the head of the governments in five separate provinces, and men at the head of the parties opposing them, all agreed at the same time to sink party differences for the good of all, and did not shrink, at the risk of having their motives misunderstood, from associating together for the purpose of bringing about this result. (Cheers.)

Familiar Talks on Science, Volume 1, 1899, p. V
(See Charles Babbage's for a similar commentary on miracles)
Nature's Miracles (1900)

Source: Flora and Ulysses: The Illuminated Adventures

Chantal to Dr. La Pérouse, p. 188
La joie (Joy) 1929

"Passages from the life of a philosopher", Appendix, p. 489
Passages from the Life of a Philosopher (1864)

That writers do not always mean the same thing when treating of miracles is perfectly clear; because what may appear a miracle to the unlearned is to the better instructed only an effect produced by some unknown law hitherto unobserved. So that the idea of miracle is in some respect dependent upon the opinion of man. Much of this confusion has arisen from the definition of Miracle given in Hume's celebrated Essay, namely, that it is the "violation of a law of nature." Now a miracle is not necessarily a violation of any law of nature, and it involves no physical absurdity. As Brown well observes, "the laws of nature surely are not violated when a new antecedent is followed by a new consequent ; they are violated only when the antecedent, being exactly the same, a different consequent is the result;" so that a miracle has nothing in its nature inconsistent with our belief of the uniformity of nature. All that we see in a miracle is an effect which is new to our observation, and whose cause is concealed. The cause may be beyond the sphere of our observation, and would be thus beyond the familiar sphere of nature; but this does not make the event a violation of any law of nature. The limits of man's observation lie within very narrow boundaries, and it would be arrogance to suppose that the reach of man's power is to form the limits of the natural world. The universe offers daily proof of the existence of power of which we know nothing, but whose mighty agency nevertheless manifestly appears in the most familiar works of creation. And shall we deny the existence of this mighty energy simply because it manifests itself in delegated and feeble subordination to God's omnipotence?
"Passages from the life of a philosopher", Appendix: Miracle. Note (A)
Passages from the Life of a Philosopher (1864)