The city being taken as the heart of London, there are two main arteries by which its blood is put in circulation. One is Holborn, prolonged by Oxford Street and the Uxbridge Road, so as to make almost a straight line through the metropolis, continued eastward from Aldgate along the great Whitechapel highway, in all a distance of some ten miles for a bee that had spare time to measure it from Bow Bridge to Hammersmith.