The popular instrument of the nineteenth century has been the pianoforte, the result of an evolution having its beginning more than six centuries back. It is impossible in the present state of knowledge to trace all the steps through which this remarkable instrument has reached its present form. In the Assyrian sculptures discovered by Layard, there are instruments apparently composed of metal rods or plates, touched by hammers, upon the same general principle as the toy instrument with glass plates, or the xylophone composed of wooden rods resting upon bands of straw. In these the use of the hammer for producing the tone is obvious. In the Middle Ages there was an instrument called the psaltery, apparently some sort of a four-sided harp strung with metal strings. The evidence upon this point is rather indistinct. Still later there is the Arab santir (p. 114). This was a trapeze-shaped instrument, composed of a solid frame, sounding board and metal wires struck with hammers. This instrument still exists in Germany under the name of _Hackbrett_, or the dulcimer. As now made, each string consists of three wires tuned in unison. It is played by means of leather hammers held in the hand. The difficulty of adapting this instrument to the keyboard consisted in the fact that if the hammers were connected with the keys, they would be under the strings instead of above them, and this difficulty for a long time proved insurmountable. [Illustration: Fig. 68. SPINET. (Showing the disposition of the strings, bridges, etc. Dresden, 1590.)]