1From Benjamin Franklin to Mary Stevenson, 11 June 1760 (Franklin Papers)
ALS : Library of Congress ’Tis a very sensible Question you ask, how the Air can affect the Barometer, when its Opening appears covered with Wood? If indeed it was so closely covered as to admit of no Communication of the outward Air to the Surface of the Mercury, the Change of Weight in the Air could not possibly affect it. But the least Crevice is sufficient for the Purpose; a Pinhole will...