The following account of this device, supposed to be from the pen of Benjamin Franklin, indicates fully why it was adopted, and will be found in the _American Archives_, vol. iv. p. 468.
"I observe on one of the drums belonging to the marines now raising, there was painted a rattlesnake, with this motto under it, 'Don't tread on me.' As I know it is the custom to have some device on the arms of every country, I suppose this may have been intended for the arms of America; and, as I have nothing to do with public affairs, and as my time is perfectly my own, in order to divert an idle hour, I sat down to guess what could have been intended by this uncommon device. I took care, however, to consult, on this occasion, a person who is acquainted with heraldry, from whom I learned that it is a rule, among the learned in that science, 'that the worthy properties of the animal, in the crest-born, shall be considered;' he likewise informed me that the ancients considered the serpent as an emblem of wisdom; and, in a certain attitude, of endless duration--both which circumstances, I suppose, may have been had in view. Having gained this intelligence, and recollecting that countries 'are sometimes represented by animals peculiar to them,' it occurred to me that the rattlesnake is found in no other quarter of the world beside America, and may, therefore, have been chosen on that account to represent her.
"But then, 'the worthy properties' of a snake, I judged, would be hard to point out. This rather raised than suppressed my curiosity, and having frequently seen the rattlesnake, I ran over in my mind every property by which she was distinguished, not only from other animals, but from those of the same genus or class of animals, endeavoring to fix some meaning to each, not wholly inconsistent with common sense.
"I recollected that her eye excelled in brightness that of any other animal, and that she has no eye-lids. She may, therefore, be esteemed an emblem of vigilance. She never begins an attack, nor, when once engaged, ever surrenders. She is, therefore, an emblem of magnanimity and true courage. As if anxious to prevent all pretensions of quarrelling with her, the weapons with which nature has furnished her she conceals in the roof of her mouth; so that, to those who are unacquainted with her, she appears to be a defenceless animal; and even when those weapons are shown and extended for defence, they appear weak and contemptible; but their wounds, however small, are decisive and fatal. Conscious of this, she never wounds till she has generously given notice, even to her enemy, and cautioned him against the danger of treading on her. Was I wrong sir, in thinking this a strong picture of the temper and conduct of America?