Structure of the Earth discontinuity (a second order discontinuity). The uppermost mantle together with the crust constitutes the lithosphere. The crust-mantle boundary occurs as two physically different events. First, there is a discontinuity in the seismic velocity, which is most commonly known as the Mohorovičić discontinuity or Moho. The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain no feldspars (below). Second, in oceanic crust, there is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites, which has been observed from deep parts of the oceanic crust that have been
Copia: Foundations of the Abundant Style on Quintillian's rhetorical guide, "Institutio Oratoria". The first chapter of book 10 in Quintillian's "Oratoria" is titled ""De copia verborum"". This is quite possibly where Erasmus received his most direct inspiration for the book. In that 10th chapter, Quintillian declined to give examples for employing the abundant style, on the grounds that each individual case requires a unique solution. This left the door open for Erasmus to detail the abundant style in "Copia". Erasmus acknowledges Quintillian in the preface, and borrows from him (and other classical authors) throughout "Copia", sometimes citing, sometimes not. As further revisions of "Copia" are printed,