Sentence:  In the <WSD>Neptunian</WSD> ſyſtem it is ſuppoſed that the poſitions of the ſtrata have been determined, partly by the figure of the baſe or ground on which they have been depoſited, and partly by their depoſition having been a ſpecies of cryſtallization. 
Meaning of the word marked with <WSD> tags:  Of, pertaining to, or supporting (rocks were formed from the crystallisation of minerals in the early Earth's oceans).