Knowledge and Inventions 



that the big black hand on the white-painted 

 dial could be seen distinctly and the tempera- 

 ture 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 posi- 

 tion. It was regarded as a great wonder by 

 the neighbors and even by my own all-Bible 

 father. 



Boys are fond of the books of travelers, and 

 I remember that one day, after I had been 

 reading Mungo Park's travels in Africa, mother" 

 said: "Weel, John, maybe you will travel like 

 Park and Humboldt some day." Father over- 

 heard her and cried out in solemn deprecation, 

 I 259 1 



