At 15, John A. Spencer of Revere, Mass., was a mill-hand in a Maine lumber camp. He worked with the night shift and part of his job was to keep the boiler simmering. The boiler had a rounded clean-out door; and when John heaped up a hot fire, this door would go Crick! outward, convex like a bubble. When the fire cooled down, Crack! would go the boiler door, back inward, concave like a saucer.
John Spencer grew to years of discretion and mechanical knowledge. Re- cently, the U. S. Patent Office issued to him a...
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