The origin of the vast city whose population now approximates four millions is obscure. It was a British settlement before the Romans came to England, and its name of Llyn Dyn, the "City of the Lake," was transformed by the conquerors into Londinium. When Caesar crossed the Thames he thought the settlement of too little importance for mention, and it does not seem to have been occupied as a Roman station until a century afterwards, and was not walled round until A.D. 306. The old wall was about three miles in circumference, beginning near the present site of the Tower, and some slight traces of it remain. The "London Stone" on Cannon Street was the central stone or _milliarium_ from which distances were measured and the great Roman highways started. A worn fragment of this stone, protected by iron bars, now stands against the wall of St. Swithin's Church. When Jack Cade entered London, Shakespeare tells us, he struck his sword on this stone and exclaimed, "Now is Mortimer lord of this city." Wren caused it to be encased, for protection, with a new stone hollowed for the purpose; it now stands very near its original position. London in the sixth century became the capital of the Saxon kingdom of Essex, and in the ninth century the Danes destroyed it. King Alfred a few years afterwards rebuilt London, but it stood barely seven years when it was burned. Finally, it was again rebuilt, and again captured by the Danes, Canute setting himself up as king there. Some relics of these Danes remain. St. Olaf was their saint, and Tooley Street is but a corruption of his name. They had a church and burial-place where now St. Clement-Danes stands awry on the Strand--a church that is of interest not only on its own account, but for the venerable antiquity it represents. The Saxons drove out the Danes, and the Normans in turn conquered the Saxons, the Tower of London coming down to us as a relic of William the Conqueror, who granted the city the charter which is still extant. Henry I. gave it a new charter, which is said to have been the model for _Magna Charta_. In the twelfth century London attained the dignity of having a lord mayor. It sided with the House of York in the Wars of the Roses, and in Elizabeth's reign had about one hundred and fifty thousand population, being then about two miles south of Westminster, with fields between, and having the Tower standing apart from the city farther down the Thames. The plague devastated it in 1665, carrying off sixty thousand persons, and next year the Great Fire occurred, which destroyed five-sixths of the city within the walls, and burned during four days. This fire began at Pudding Lane, Monument Yard, and ended at Pie Corner, Giltspur Street. To commemorate the calamity the Monument was erected on Fish Street Hill, on the site of St. Margaret's Church, which was destroyed. It is a fluted Doric column of Portland stone, erected by Wren at a cost of $70,000, and is two hundred and two feet high.