Nicolas Steno 347th Birthday Google Doodle. Steno's life and work has been studied, in particular in relation to the developments in geology in the late nineteenth century. Steno, in his Dissertationis prodromus of 1669 is credited with three of the defining principles of the science of stratigraphy: the law of superposition: '...at the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed'; the principle of original horizontality: 'Strata either perpendicular to the horizon or inclined to the horizon were at one time parallel to the horizon'; the principle of lateral continuity: .