The National Geographic Magazine, Volume 92National Geographic Society, 1947 - Geography Indexes kept up to date with supplements. |
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Page 422
... watches in Memorial Hall , Philadelphia , is the clock - watch believed to have been made by Peter Henlein and to be the oldest portable clock - watch in existence ( page 424 ) . This was the first attempt to get the works of a clock ...
... watches in Memorial Hall , Philadelphia , is the clock - watch believed to have been made by Peter Henlein and to be the oldest portable clock - watch in existence ( page 424 ) . This was the first attempt to get the works of a clock ...
Page 427
... watch is less than 1/3 the diameter of an average human hair ( page 407 ) . The standard unit of measure in a watch is 1 / 10,000 of an inch . This means that each one of the 100 or more parts when tested must meet this accuracy . Some ...
... watch is less than 1/3 the diameter of an average human hair ( page 407 ) . The standard unit of measure in a watch is 1 / 10,000 of an inch . This means that each one of the 100 or more parts when tested must meet this accuracy . Some ...
Page 428
... Watch Company's " time- microscope , " the balance wheel of the watch is observed . At accurate split - second intervals a revolv- ing reflector flashes a light on the watch's balance wheel , and if its speed is the same as the ...
... Watch Company's " time- microscope , " the balance wheel of the watch is observed . At accurate split - second intervals a revolv- ing reflector flashes a light on the watch's balance wheel , and if its speed is the same as the ...
Contents
Adventures with the Survey Navy By Irving Johnson 131 | xxi |
Carnival in San Antonio Texas By Mason Sutherland With 19 illustrations in color | xxvii |
Desert River San Juan Through Navajo Land By Alfred M Bailey With 11 illus | xxxiii |
Copyright | |
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