“Confidence is a plant of slow growth in an aged bosom.”

Letter to Bushrod Washington http://en.wikipedia.org/wiki/Bushrod_Washington (15 January 1783)
1780s

Source: A Short History Of The English Law (First Edition) (1912), Chapter I, Old English Law, p. 3

[Ugo Bardi, 2017, The Seneca Effect: Why growth is slow but collapse is rapid, 7, Springer, 1612-3018, 10.1007/978-3-319-57207-9]
Other works

Letter to James Madison http://teachingamericanhistory.org/library/document/letter-to-james-madison-12/ (2 March 1788)
1780s

Bell Telephone Talk (1901)
Context: You cannot force ideas. Successful ideas are the result of slow growth. Ideas do not reach perfection in a day, no matter how much study is put upon them.

The Complete Neurotic's Notebook (1981), Unclassified

Source: The Geological Evidences of the Antiquity of Man (1863), Ch.20, p. 393
Context: I endeavoured to sketch out (and it was, I believe, the first systematic attempt to accomplish such a task) the laws which govern the extinction of species, with a view of showing that the slow, but ceaseless variations, now in progress in physical geography, together with the migration of plants and animals into new regions, must, in the course of ages, give rise to the occasional loss of some of them, and eventually cause an entire fauna and flora to die out; also, that we must infer, from geological data, that the places thus left vacant from time to time, are filled up without delay by new forms, adapted to new conditions, sometimes by immigration from adjoining provinces, sometimes by new creations. Among the many causes of extinction enumerated by me, were the power of hostile species, diminution of food, mutations in climate, the conversion of land into sea, and of sea into land, &c.

Source: The Spanish Drama (1846), Ch. 2