Louis Bertrand, a learned mathematician, was born at Montpellier in 1688, and entered the order of the Jesuits in 1703. At first he was a student of literature, but afterwards devoted himself entirely to mathematics and natural philosophy. He wrote a Traité de la Pésanteur Universelle, Paris, 1724; Mathématique Universelle; Le plan du Mathématique abrégé, and other works. But the work which attracted most attention at the time was his Optique des Couleurs, or treatise on the melody of colours, a subject which he endeavoured to illustrate by a Clavelin Oc- laire, or ocular harpsichord. The treatise and the illustration were, however, quickly forgotten. He also published a critical account of the system of Sir Isaac Newton in French. Castel died in 1757.

CASTEL-A-MARE, or CASTELLAMARE, a city and seaport on the gulf of Naples, 17 miles S.E. of the city of that name. It is pleasantly situated on the lower slopes of a hill, and along a sheltered beach, commanding an extensive view of the Bay of Naples from Vesuvius to Misenum. It stands near the site of the ancient Stabiae, destroyed by Sulla in the social war, but which continued to exist as a small place till A.D. 79, when it was overwhelmed along with Pompeii and Herculaneum by the great eruption of Vesuvius. It was here that the elder Pliny met his death on that occasion. The city takes its name from the castle which was erected by Frederick II., surrounded by walls and towers in the thirteenth century by Charles I. of Anjou, and strengthened by additional fortifications by Alfonso I. of Aragon. It is the seat of a bishopric, and has a royal palace, cathedral, several churches and convents, military hospital, barracks, handsome quay, royal arsenal, and dockyard, where the large ships of the Neapolitan navy are built. There are manufactures of linen, silk and cotton goods, and leather. The port is small, and divided by two forts. The hill immediately above the town is covered with villas and casini; among which is the royal Casino of Quisisana, more remarkable for its fine prospect than for its magnificence as a palace. The town is connected by railway with Naples. Pop. 18,000.

CASTEL-A-MARE, a seaport-town of Sicily, on the gulf of the same name, in the province of Trapani. It is a small dirty town, but has a considerable export trade in wine, fruit, grain, &c. Pop. 6000.