the instrument which sustains the tension of the strings, which in full to large-sized pianos is not less than from six to twelve tons, and it is a matter of prime necessity that the portions which serve as a strut or stretcher between the ends of the strings, and which are to resist this enormous pull, must be made correspondingly strong and rigid, since by any gradual yielding under the pull of the strings, their lengths and tensions, and hence their tone, must undergo proportionate change.  In the old pianos, the frames were of wood, and it was impossible to use any but small, short strings, for the reason given above.  Fullness and power were not to be thought of, and builders were obliged to confine themselves to securing truthfulness of tone.  A multitude of causes, among which were the changes in the weather, combined to render it impossible to keep the old-fashioned instrument in tune.  It was this defect which first attracted the attention of Jonas Chickering, and his first endeavor was to produce an instrument which would withstand the climatic changes which were so troublesome to the old ones.  He was fully aware of the fact that the piano trade in this country was then so unimportant that it offered but little inducement to a man who could manufacture only the old instrument; but he believed that by producing an instrument of better proportions, and one fuller, richer, and more lasting in tone, he could create a demand for it which would insure the sale of all he could manufacture.  His hope of success lay not in the old, but in an improved and nobler instrument.  That he was correct in his belief, the magnificent instrument of to-day which bears his name, and the lucrative business he has left to his sons, amply demonstrate.  Others besides himself were working for the same end, and he knew that he would have to bear the test of determined and intelligent competition.  He applied himself to his purpose with enthusiasm.  He carefully studied the theory of atmospheric vibration and musical combination, as well as an application of the principles of mechanical philosophy to the construction of the instrument.  He went deep into the science involved in his work, into the philosophy of melody.  Passionately devoted to music, he was ambitious of placing that which has been so truly called “the king of instruments” within the reach of all lovers of harmony, and to give them the best instrument that human invention could produce—­an instrument which should not only withstand atmospheric changes, but which should yield the richest, fullest volume of melody, with the least exertion to the performer.  His progress was slow, but it was sure.  Beginning with an improvement in the action, he accomplished, in a great measure (in 1838), his plan for preserving the permanence and purity of the tone of the instrument by casting the entire iron framing with the parallel bars in one piece.  Iron had for some time before this been in general use for framing, but the frame