In his 1787 book, Notes on the State of Virginia, Jefferson launched into a discussion of the climate of both his home state and America as a whole. Near the end of a brief chapter addressing wind currents, rain and temperature, he presented a series of tentative conclusions: "A change in our climate... Snows are less frequent and less deep....The elderly inform me the earth used to be covered with snow about three months in every year. The rivers, which then seldom failed to freeze over in the course of the winter, scarcely ever do so now." Concerned about the destructive effects of this warming trend, Jefferson noted how "an unfortunate fluctuation between heat and cold" in the spring has been “very fatal to fruits.”..(Spring Cold snaps)...