IT is not a tower at all, as we reckon towers, you must know, but a walled town upon the banks of the Thames, in the very heart of London. Hundreds of years ago, when what is now this great city was only moor and marsh, the Romans built here--a castle, perhaps. Only a bit of crumbling wall, of mouldering pavement, remain to tell the story. When the Normans came in to possess the land, William the Conqueror erected upon this spot a square fortress, with towers rising from its four corners. Every succeeding monarch added a castle, a tower, a moat, to strengthen its strength and extend its limits, until, in time, it covered twelve acres of land, as it does to this day. Here the kings and queens of England lived in comfortless state, until the time of Queen Elizabeth, having need to be hedged about with something more than royalty to insure safety. Times have changed; swords have been beaten into ploughshares; and where the moat once encircled the tower wall, flowers blossom now. The dungeons that for centuries held prisoners of state do not confine any one to-day; and the strongholds that guarded the person of England's sovereign keep in safety now the jewels and the crown. There are round towers, and square towers, and, for anything I know, three-cornered towers, each with its own history of horrors. There are windows from which people were thrown, bridges over which they were dragged, and dark holes in which they were incarcerated. [Illustration: "A dozen umbrellas were tipped up; the rain fell fast upon a dozen upturned, expectant faces." Page 57.]