The large mass of nebulosity between t, and e Cygni, and extending towards Aquila, should be slightly darker, whereas on Plate IV. (General View) it isnbsp;rather too dark. The region between y and ß Cygni shows the lanes separating thenbsp;different patches of nebulosity too plainly. Yet I consider these divisions verynbsp;conspicuous, and am surprised that they have never been drawn before.

The preceding boundary of Scutum I have drawn too distinctly ; the nebulosity should be more extended in that direction. Yet the general shape of the region innbsp;Scutum will, I think, be found fairly correct. It obviously shows that the name ofnbsp;the constellation was not inaptly derived from the shield-like patch of Milky Waynbsp;light.

The most brilliant portions in the whole section are, in order of brightness, the ray from ß to e Scuti, the region north of a Cygni, and the ray proceeding to thenbsp;south from y Cygni.

• 7. nbsp;Plate IL—Section ‘Cassiopeia.’ The Galaxy decreases considerably innbsp;brightness on entering Cepheus. The only spot which almost equals the regionnbsp;north of a Cygni in intensity is the cluster Persei ; next in brightness comes thenbsp;spot near 496 O X. Both these markings, especially the former, did not come outnbsp;sufficiently intense in the plate as finally struck off.

I found the delineation of this section connected with considerable difficulty, owing to the faintness of the nebulosity and the brilliancy of the stars which itnbsp;surrounds ; yet I think that the main features of my drawing will be readily confirmed.nbsp;Towards the north the Milky Way embraces the Pole star, and towards the southnbsp;it sends out numerous feelers, the most extended of which reaches y Arietis.

• 8. nbsp;Plate III.—Section ‘Auriga, Gemini, Monoceros.’ The remarks made atnbsp;the beginning of paragraph 6 apply with special force to this section. In fact, tonbsp;such an extent are the lanes in it filled in with nebulous light, that this portion ofnbsp;the Galaxy appears at first to be essentially one broad stream of uniform luminosity.nbsp;In order, therefore, to bring out the detail which long-continued examination reveals,nbsp;the contrast had to be not inconsiderably exaggerated. The gradation of thenbsp;different parts is well represented in the lithograph, and the intensity of the wholenbsp;section in proportion to the remaining parts of the Galaxy is satisfactorily shown onnbsp;Plate IV.

On the preceding side the Milky Way sends out feelers as far as Præsepe, on the following one it embraces the Pleiades, the Hyades, and Orlon certainly as farnbsp;as to TT^. These feelers and the sweep through to tt® Orionis, as well as somenbsp;other outlying detail, have been lost in the final printing-off. As they are, however,nbsp;sufficiently indicated on Plate IV., it would be advisable, before use, to compare Platesnbsp;I. to III. with Plate IV., and, by means of the stump, to insert into the former thenbsp;detail only shown in the latter. It was obviously lost mainly through our attempt tonbsp;indicate in the sections the fainter parts of the Galaxy in their correct proportionsnbsp;of intensity. It should be added that the cluster in Perseus on Plate II. shouldnbsp;be inserted in two distinct patches, the places of which may be taken fromnbsp;Argelander’s maps.

My remarks are here based on the comparison of one set of plates only with the original drawing. It is, of course, possible—or even probable, since all thenbsp;features now missing were shown in the proofs—that a portion only of the wholenbsp;edition will require the slight corrections indicated above.

• 9. nbsp;Plate IV.—General View. The whole of the detail on this plate isnbsp;deliberately exaggerated—a little too much so, perhaps, for correct gradation in thenbsp;region Cepheus-Cassiopeia.

• 10. nbsp;In concluding, I take this opportunity of expressing my conviction thatnbsp;the admirable photographs of the Milky Way recently produced by Messrs. Barnard,nbsp;Russell amp; Wolf in no way supersede careful hand-drawing of what is seen by thenbsp;naked eye. The photograph obviously gives a section of the Galaxy lying muchnbsp;beyond what we see without optical means, since it resolves into stars what to thenbsp;naked eye appears as unresolved nebulosity. Thus the hope appears justified thatnbsp;by superimposing the drawing on the photograph some knowledge of the structurenbsp;of the Milky Way in the line of sight may be obtained. To assist myself in carryingnbsp;the subject further in this direction, I have already begun to photograph the Galaxynbsp;systematically, giving each plate the same exposure, so as to penetrate into space allnbsp;along the Milky Way to the same depth. Before this work is carried through, somenbsp;years must necessarily elapse. In the meantime, much aid could be given by naked-eyenbsp;observers by correcting the drawing laid here before them. For, though it is thenbsp;result of five years’ labour, still I wish it to be regarded as a first approximation onlynbsp;to a really accurate representation of the naked-eye view of the Milky Way.

OTTO BOEDDICKER.

Birr Castle Observatory, Parsonstown :

December 6, 1891.