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would make the position of Icaromenippus impossible. But artists have so often and so persistently claimed the right to ignore this fact that it would be discourteous to maintain this objection.

Pages 15 and 16.—The pictures of Tycho Brahe's observatory and sextant are from the beautiful collections made by Professor Weinek of Prague, and published in the observatory volumes.

Page 19.—The Earth and Halley's Comet. This drawing originally appeared in the Illustrated London News for Sept. 25, 1909, and is reproduced by kind permission.

Page 36.—The Great Comet of 1858 is from Telescope Teachings by the Hon. Mrs. Ward (Groombridge & Sons, 1859), a book with numerous beautiful illustrations much prized by our fathers and grandfathers.

Page 39.—The Return of Halley to see his Comet is, as stated in the text, from a picture in the possession of Mr. H. P. Hollis, of the Royal Observatory, Greenwich, and is reproduced by his kind permission.

Page 42.—Changes in a Comet's tail by E. E. Barnard. This is not the pair of pictures shown on the screen at the lectures, but is a triumph of Professor Barnard's skill given in the Astrophysical Journal, Vol. XXII., Plate VIII. (facing p. 251).

Page 48. Wreck of the Searchlight apparatus. This illustration is from p. 380 of Pearson's Magazine, in the volume July-December, 1907; and is reproduced by kind permission of the Editorial Manager. The author is fortunate enough to possess the original pair of drawings for this excellent story.

Pages 60 and 61.—Transit of Venus. These illustrations are reproduced (by permission of the Delegates of the Clarendon Press) from Chambers's Handbook of Astronomy.

Page 63.—Horrox observing the Transit of Venus. This is reproduced, by kind permission of Mr. Napier Clark, formerly of Southport and now of 16 Hallhead Road, Edinburgh, from a picture in his possession painted by W. R. Lavender. There is no description or portrait of Horrox in existence, and the representation is therefore purely imaginary. The observation was made at the village of Much Hoole, near Southport, on Nov. 24 [O.S.], 1639. Horrox was at that time about twenty. The