_C_ is the key; _d_ is a pilot, centered at _dd_ to give the blow, by means of a carrier, _e_, holding the hopper, _g_, which delivers the blow to the hammer, _o_, by the thrust of the hopper, which escapes by forward movement after contact with a projection from the hammer covered with leather, answering to the notch of the English action. This escapement is controlled at _x_; a double spring _il_, pushes up a hinged lever, _ee_, the rise of which is checked at _pp_, and causes the second or double escapement; a little stirrup at the shoulder of the hammer, known as the "repetition" pressing down _ee_ at the point, and by this depression permitting _g_ to go back to its place, and be ready for a second blow before the key has been materially raised. The check _p_ in this action is not behind the hammer, but before it, fixed into the carrier, _e_, which also, as the key is put down, brings down the under damper. (Hipkins.)] The instruments were still small, and strung with small wires; nevertheless, there was a tendency toward increased compass, which, by the beginning of the nineteenth century, led the Broadwoods, of London, to attempt a grand piano with six octaves' compass. But they found that the wrest plank (in which the tuning strings are placed), was so weakened by the extension that the treble would not stand in tune. In order to strengthen the instrument, he introduced the iron tension bar. This, like nearly all of the English improvements of the piano during the first quarter of the nineteenth century, was in the direction of greater solidity, and better resisting power to the pull of the strings. Upon the artistic side, Sebastian Erard in 1808 patented his grand action, which, with very slight improvements, still remains the model of what a piano action should be. Fig. 74 shows this action and its parts. [Illustration: Fig. 75. THE STEINWAY IRON FRAME. (Showing the disposition of the sounding board, bridges, etc.)]