There are quite a few literary devices used in The Autobiography of Benjamin Franklin.
Assonance, typically seen in poetry, is the repetition of a vowel sound within a line. The opening of the text offers an example of assonance.
Dear son: I have ever had pleasure in obtaining any little anecdotes of my ancestors.
Here, the "a" sound in anecdotes and ancestors is repeated.
Alliteration is similar to assonance, but a consonant sound is repeated. In the second line of the autobiography an example of alliteration is found.
You may remember the inquiries I made among the remains of my relations when you were with me in England, and the journey I undertook for that purpose.
The "r" sound in remember, remains, and relations is repeated and exemplifies alliteration.
Imagery is the use of words which come to allow a reader to create a mental picture of what is being described. Many times, imagery appeals to the reader's senses (taste, touch, sight, sound, and smell).
In chapter two, the following excerpt has wonderful imagery:
There were canoes on the shore, and we made signs, and hallow'd that they should fetch us; but they either did not understand us, or thought it impracticable, so they went away, and night coming on, we had no remedy but to wait till the wind should abate; and, in the meantime, the boatman and I concluded to sleep, if we could; and so crowded into the scuttle, with the Dutchman, who was still wet, and the spray beating over the head of our boat, leak'd thro' to us, so that we were soon almost as wet as he. In this manner we lay all night, with very little rest; but, the wind abating the next day, we made a shift to reach Amboy before night, having been thirty hours on the water, without victuals, or any drink but a bottle of filthy rum, and the water we sail'd on being salt.
The bolded passages appeal to the senses of the reader. One can easily paint a picture of soaked men, thirsty and beaten by the water and wind. The mentioning of salt can leave a reader's mouth dry and while their face will feel dried out and stretched from the salt's drying nature.