Another form of literature, in which Rome became pre-eminent, first began in this era,--the writing of familiar letters. It was natural that a correspondence should be maintained among intimate friends and members of an active social circle, separated for years from one another by military service, or employment in the provinces; and the new taste for literature would induce the writers to give form and finish to these compositions, so that they might be interesting not only to the persons addressed, but to all the members of the same circle. The earliest compositions of this kind of which we read, are the familiar letters in verse ('Epistolas versiculis facetis ad familiares missas' Cicero calls them) written to his friends by the brother of Mummius, during the siege of Corinth[335]. That these had some literary value may be inferred from the fact that they survived down to the age of Cicero, and are spoken of in the letters to Atticus, as having often been quoted to him by a member of the family of Mummii. One of the earliest satires of Lucilius appears to have been a letter written to Scipio after the capture of Numantia; and several of his other satires were written in an epistolary form. How happily the later Romans employed this form in prose and verse is sufficiently proved by the letters of Cicero and Pliny, and the metrical Epistles of Horace. This era also saw the beginning of the critical and grammatical studies which flourished through every period of Roman literature, and continued long after the cessation of all productive originality. This critical effort was a necessary condition of the cultivation of art by the Romans. The perfection of form attained by the great Roman poets of a later time was no exercise of a natural gift, but the result of many previous efforts and failures, and of much reflection on the conditions which had been, with no apparent effort, fulfilled by their Greek masters. Neither did their language acquire the symmetry, precision, and harmony, which make it so effective a vehicle in prose and verse, except as the result of assiduous labour. The natural tendency of the spoken language was to rapid decomposition. This was first arrested by Ennius, who cast the literary language of Rome into forms which became permanent after his time. Among his poetic successors in this era Accius and Lucilius made critical and grammatical studies the subjects of some of their works. Lucilius was a contemporary and friend of the most famous of the early grammarians, Aelius Stilo, the critic to whom is attributed the saying that 'if the muses were to speak in Latin, they would speak in the language of Plautus.' Critical works in trochaic verse were written by Porcius Licinus, and Volcatius Sedigitus, who appear to have been the chief authorities from whom later writers derived their information as to the lives of the early poets. It is characteristic of the want of spontaneousness in Latin