Sands of time

Who leaves foot prints behind? My answer to this in depth question is that all of us do. It is impossible to not leave foot prints on the sands you have once walked, it's how long it'll last that counts. Some foot prints are deeper than the others, and can bare through the tide waves's merciless pounds. The others are shallow and barely visible, those are the footprints that will erode by the faintest peck of the sea breeze. Yet as all may have known, one day, these foot prints will all get erased, deep or shallow. One day every single one of us will be forgotten, famous or not. This is not what this journal entry is supposedly about, I simply tried to express a little more. I do apologize for that. Anyway, some historical figures that reminded me that people can accomplish great things are: Newton...etc. You get my idea. THese people had accomplished great things, and left very deep footprints in the sand of humanity. I am unsure of the literary device Longfellow used with " leave behind footprints", but I'm guessing that it is a...? As I have previously stated, I and everyone will leave foot prints through time. Though some may think it's simply a clever play of words, it is my true belief. As in for how deep? I don't know. I really truly have no idea. You the people  are  going to have to measure it, I suppose.