I BEG leave to observe that the very useful method of distributing astronomical predictions over a given geographical area alluded to in NATURE, vol. xiii., page 71, and ascribed there to Mr. W. S. B. Woolhouse, was already proposed by my father, J. J. von Littrow, in his treatise, “Darstellung der Sonnenfinsterniss vom 7 September, 1820,” Pest, 1820, as well as in the Berliner Astronomisches Jahrbuch, for 1821, page 116, and 1822, page 145; subsequently in his “Theoretische und practische Astronomie,” Wien, 1821, part ii., page 280; and last in his “Vorlesungen uber Astronomie,” Wien, 1830, part i., page 306. Since then numerous applications have been made thereof. My father expressed the well-founded desire that in the astronomical almanacs formulae might be given similar to that communicated in NATURE.