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]
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.
Pages:
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243