 Steno's ideas still form the basis of stratigraphy and were key in the development of James Hutton's theory of infinitely repeating cycles of seabed deposition, uplifting, erosion, and submersion.Steno gave the first accurate observations on a type of crystal in his 1669 book ""De solido intra solidum naturaliter contento"".The principle in crystallography, known simply as "Steno's law", or "Steno's law of constant angles" or the "first law of crystallography", states that the angles between corresponding faces on crystals are the same for all specimens of the same mineral.