"These mosaics, like the ones we shall see at the Houses of Parliament, were not first made and then put up on the walls as were those such as Salviati and other Venetians shipped from Venice," explained Mr. Cabot. "No, these were made directly upon the walls, the pieces of glass being pressed into prepared areas of cement spread thickly upon the brickwork of the building. The designs are simple, large and effective figures being preferred to smaller and more intricate patterns. Millions of pieces have been used to make the pictures, and if you will notice carefully you will see that they have the rough surface which catches the light as do all the early Venetian mosaics." Giusippe nodded. "There must also be some fine old glass windows in London," he speculated. "Aren't there, Mr. Cabot?" "Yes, some varieties that you did not have in Venice, too," declared Uncle Bob. "You see other people did invent something, Giusippe. Here in England in some of the older houses there are windows made of tiny pieces of white glass leaded together; people were not able at that time to get large sheets of glass such as we now use, and I am not sure that these windows made of small leaded panes were not prettier. Then you will find other windows made from what we call bull's eye glass. These bull's eyes were the centers or waste from large discs of crown glass after all the big pieces possible had been cut away. As most glass comes now in sheets crown glass is little made, and therefore we find bull's eyes rare unless manufactured expressly to imitate the antique roundels." "Of course there is lots of old stained glass in England, isn't there, Uncle Bob?" Jean ventured. "Yes, indeed. I am sorry to say, however, that much of it has been destroyed before the public realized its value. At Salisbury Cathedral, for instance, some of the fine old glass was taken down and beaten to pieces in order that the lead might be used. At Oxford rare Gothic windows were removed and broken up to give room for the more modern work of the Renaissance. But you will still find at Canterbury and in many other of the English churches stained glass which has escaped destruction and come down to us through hundreds of years. And speaking of how such things have been preserved I must tell you the wonderful story of the east window in St. Margaret's Chapel at Westminster." "Oh, do tell us!" begged Jean. "I love stories."