In consequence of a letter received from Dr. C.L. Gerling in the summer of 1847, urging the desirability of observing the planet Venus about the time when it is stationary, in order to obtain a better value of the solar parallax than Encke's, which was then generally adopted, Captain James M. Gillis, of the United States Navy, conceived of an astronomical expedition to Chili for the purpose of making the required observations in conjunction with the United States Naval Observatory at Washington.