In a period of which so much is known, and of which the materials for additional knowledge are so abundant, as is the case with the eighteenth century, the writer of a handbook sees from the first that a very great deal, of even important matters, will have to be omitted: and one of his chief difficulties will be to decide which topics must be selected in order to give the reader an intelligible and coherent picture - faithful, as far as it goes - of the period as a whole.