1To Benjamin Franklin from James Alexander, 29 January 1753 (Franklin Papers)
Copies of letter and enclosure: New-York Historical Society The rare transits of Venus across the sun’s surface were among the most important astronomical occurrences in the eighteenth century because they offered astronomers opportunities to calculate the solar parallax—the angle subtended at the sun by the earth’s radius—and thus not only provided a basis for computing the actual distance...
2To Benjamin Franklin from James Alexander, 1753 (Franklin Papers)
Printed in Benjamin Franklin, Experiments and Observations on Electricity (London, 1769), pp. 280–1. If I remember right, the Royal Society made one experiment to discover the velocity of the electric fire, by a wire of about four miles in length, supported by silk, and by turning it forwards and backwards in a field, so that the beginning and end of the wire were at only the distance of two...