"All this we have learned to make allowance for. But the poor old clockmakers had to gather these facts by long and tiresome experiment. At length brass pendulums which, they discovered, made the most trouble, were replaced by those of iron or lead which, being of softer material, expanded and contracted more readily. In our day you will sometimes see a very finely adjusted astronomical clock whose pendulum terminates in a hollow glass or iron receptacle filled with mercury, instead of the usual metal bob." "There are two of them at the store." "To be sure there are! For the moment I had forgotten that." "And all this time while clockmakers were fussing round about bobs and pendulums, did the people have to keep on running to the cathedral or the public square to find out what time it was?" "No, indeed! By 1600 you could buy for a moderate sum a clock to use at home. Not that it was a very accurate timekeeper. Nevertheless it gave a fair idea of the hour, which was all that was demanded of it," laughed McPhearson, busying himself with his screwdriver. "What sort of clocks were the first ones?" "They were not like ours, you must remember that. There was, for instance, the bird-case clock, a small chased or perforated brass affair from four to five inches square, and named because its shape suggested a cage for birds. I spoke of it before. Then there was the lantern clock. Both these varieties were made to hang on the wall and were wound by pulling down the weights that dangled from them." "They had no springs, pendulums or things?" questioned Christopher wonderingly. "That was before the days of springs. This particular type of clock, however, had a pendulum; but it was only a pendulum driven by weights showing the pendulum idea in its crudest form. Not until the long-case (or grandfather) clock made its advent into England did the pendulum, scientifically applied, come into being; and before that era many years intervened during which bracket clocks held the center of the stage." "Clocks like Richard Parsons'!" interrupted Christopher triumphantly.