Some of these darkenings may possibly have been due to an enormous development of sun-spots; but in some cases the darkness is supposed by Chladni and Schnurrer to have been caused by "the passage of meteoric masses before the sun's disc." The first observer of a transit of Venus was Jeremiah Horrocks, who observed the transit of November 24 (O.S.), 1639. He had previously corrected Kepler's predicted time of the transit from 8{h} 8{m} a.m. at Manchester to 5{h} 57{m} p.m. At the end of 1875 a marble scroll was placed on the pedestal of the monument of John Conduitt (nephew of Sir Isaac Newton, and who adopted Horrocks' theory of lunar motions) at the west end of the nave of Westminster Abbey, bearing this inscription from the pen of Dean Stanley-- "Ad majora avocatus quæ ob hæc parerga negligi non decuit" IN MEMORY OF JEREMIAH HORROCKS Curate of Hoole in Lancashire Who died on the 3{d} of January, 1641, in or near his 22{d} year Having in so short a life Detected the long inequality in the mean motion of Jupiter and Saturn Discovered the orbit of the Moon to be an ellipse; Determined the motion of the lunar aspe, Suggested the physical cause of its revolution; And predicted from his own observations, the Transit of Venus Which was seen by himself and his friend WILLIAM CRABTREE On Sunday, the 24th November (O.S.) 1639; This Tablet, facing the Monument of Newton Was raised after the lapse of more than two centuries December 9, 1874.[489]