The instrument used for writing was a reed, sharpened and split at the point, like our pens, called _calamus_. Their ink was sometimes composed of a black liquid emitted by the cuttle fish. The Romans commonly wrote only on one side of the paper, and joined one sheet to the end of another, till they finished what they had to write, and then rolled it on a cylinder or staff, hence called _volumen_. But _memoranda_ or other unimportant matters, not intended to be preserved, were usually written on tablets spread with wax. This was effected by means of a metal pencil called _stylus_, pointed at one end to scrape the letters, and flat at the other to smooth the wax when any correction was necessary. Julius Cæsar introduced the custom of folding letters in a flat square form, which were then divided into small pages, in the manner of a modern book. When forwarded for delivery, they were usually perfumed and tied round with a silken thread, the ends of which were sealed with common wax. Letters were not subscribed; but the name of the writer, and that of the person to whom they were addressed, were inserted at the commencement--thus, Julius Cæsar to his friend Antony, health. At the end was written a simple, Farewell! The Romans had many private and public libraries. Adjoining to some of them were museums for the accommodation of a college or society of learned men, who were supported there at the public expense, with a covered walk and seats, where they might dispute. The first public library at Rome, and probably in the world, was erected by Asinius Pollio, in the temple of liberty, on Mount Aventine. This was adorned by the statues of the most celebrated men. CHAPTER XXI. _Roman Houses._ The houses of the Romans are supposed at first to have been nothing more than thatched cottages. After the city was burnt by the Gauls, it was rebuilt in a more solid and commodious manner; but the streets were very irregular. In the time of Nero the city was set on fire, and more than two-thirds of it burnt to the ground. That tyrant himself is said to have been the author of this conflagration. He beheld it from the tower of Mæcenas, and being delighted, as he said, with the beauty of the flames, played the taking of Troy, dressed like an actor. The city was then rebuilt with greater regularity and splendor--the streets were widened, the height of the houses was limited to seventy feet, and each house had a portico before it, fronting the street.