My mind still running on clocks, I invented a big one like a town clock with four dials, with the time-figures so large they could be read by all our immediate neighbors as well as ourselves when at work in the fields, and on the side next the house the days of the week and month were indicated.  It was to be placed on the peak of the barn roof.  But just as it was all but finished, father stopped me, saying that it would bring too many people around the barn.  I then asked permission to put it on the top of a black-oak tree near the house.  Studying the larger main branches, I thought I could secure a sufficiently rigid foundation for it, while the trimmed sprays and leaves would conceal the angles of the cabin required to shelter the works from the weather, and the two-second pendulum, fourteen feet long, could be snugly encased on the side of the trunk.  Nothing about the grand, useful timekeeper, I argued, would disfigure the tree, for it would look something like a big hawk’s nest.  “But that,” he objected, “would draw still bigger bothersome trampling crowds about the place, for who ever heard of anything so queer as a big clock on the top of a tree?” So I had to lay aside its big wheels and cams and rest content with the pleasure of inventing it, and looking at it in my mind and listening to the deep solemn throbbing of its long two-second pendulum with its two old axes back to back for the bob.

One of my inventions was a large thermometer made of an iron rod, about three feet long and five eighths of an inch in diameter, that had formed part of a wagon-box.  The expansion and contraction of this rod was multiplied by a series of levers made of strips of hoop iron.  The pressure of the rod against the levers was kept constant by a small counterweight, so that the slightest change in the length of the rod was instantly shown on a dial about three feet wide multiplied about thirty-two thousand times.  The zero-point was gained by packing the rod in wet snow.  The scale was so large that the big black hand on the white-painted dial could be seen distinctly and the temperature read while we were ploughing in the field below the house.  The extremes of heat and cold caused the hand to make several revolutions.  The number of these revolutions was indicated on a small dial marked on the larger one.  This thermometer was fastened on the side of the house, and was so sensitive that when any one approached it within four or five feet the heat radiated from the observer’s body caused the hand of the dial to move so fast that the motion was plainly visible, and when he stepped back, the hand moved slowly back to its normal position.  It was regarded as a great wonder by the neighbors and even by my own all-Bible father.

[Illustration:  THERMOMETER]

[Illustration:  SELF-SETTING SAWMILL Model built in cellar]