Petrography rock was affixed to a microscope slide and then ground so thin that light could be transmitted through mineral grains that otherwise appeared opaque. The position of adjoining grains was not disturbed, thus permitting analysis of rock texture. Thin section petrography became the standard method of rock study. Since textural details contribute greatly to knowledge of the sequence of crystallization of the various mineral constituents in a rock, petrography progressed into petrogenesis and ultimately into petrology. It was in Europe, principally in Germany, that petrography advanced in the last half of the nineteenth century. The macroscopic characters of rocks, those
What Is Spiritism? notably: This chapter introduces some new doctrine that would be further elaborated on The Gospel According to Spiritism. What Is Spiritism? What Is Spiritism? ("Qu'Est-ce Que le Spiritisme" in French) is a brief introduction to Spiritism written by Allan Kardec in 1859, which is about a quarter of the length of The Spirits Book. Modern editions are augmented by a brief biography of the author, written by Henri Sausse, in 1896 which is mostly focused on his role in the History of Spiritism. The book is structured as a series of conferences about Spiritism, intended to quench the public curiosity