[Sidenote: 3. Areas of London and Calcutta compared.] [Sidenote: 4. Areas of London and Bombay compared.] [Sidenote: 5. Areas of London and Madras compared.] We will next consider how much space the seven million people of London take. On this slide we have two little maps, of which the lower shows in pink the ground covered by the houses of London, and above we have Calcutta shown in like manner. In the next slide the map of the houses of London is repeated, but the outline above is that of Bombay, set on its island between the harbour and the ocean. Lastly, we have a comparison of the area of London with that of Madras. In proportion to its population Madras covers a large area, for as you know there are several spaces within it planted with trees and without houses, but even Madras is small as compared with London. [Sidenote: 6. The London Docks.] Now let us start on our way through the town. The chief feature of London is the River Thames. The time was when London was only a small village on the banks of the Thames. To-day the Thames is the harbour of London, the greatest port in the world. Let us go on a little steamer along the river, and let us begin with the docks. An immense quantity of food is needed to feed seven million people. Great quantities of coal are required to keep them warm in their cold winter, and to supply gas and electricity during their long winter nights. Much material is, of course, also required for the construction of their houses and public buildings. Of all these commodities a large part is brought in by sea, and is discharged in the docks. You will remember that at the end of the last Lecture we told how the water is held up in the docks, even when the tide falls in the river. Many of the smaller steamers, however, do not go into the docks. They are able to lie in the river itself and rise and fall with the tide. [Sidenote: 7. The Tower Bridge.] When we leave the docks and proceed up the river, we come presently to a bridge, the nearest to the sea of many bridges which carry roads and railways over the Thames. This is the Tower Bridge. It is a very striking object, visible in any distant view of London, for as you see it is borne on two lofty piers, between which there is an upper and a lower way. The upper way is used by foot passengers when the lower way is lifted, as in the slide, to allow of the passage of ships with masts. [Sidenote: 8. London Bridge.]