Sentence:  But analysis, penetrating beneath the fact of Sense in search of its ideal factors, declares that this mass of marble "is" something very different from what it "appears" : its seeming continuity is broken up into <WSD>discrete</WSD> molecules, separated from each other as the stars in the Milky Way are separated ; and its seeming homogeneity is resolved into heterogeneous substances, which are themselves in all probability composite. 
Meaning of the word marked with <WSD> tags:  Separate; distinct; individual; non-continuous.