THE MOON.

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after which^we shall discuss the Moon ’s influence and use-fulness in connection with matters terrestrial.

One important fact, which deserves special attention, is thegreat success which has been achieved in recent years inlunar photography. De la Rue, Rutherfurd, Brothers, Draper,Ellery, and others, have obtained most perfect photographsof the Moon in all its various phases ; none however, in ouropinion, surpassing such an one as that by Rutherfurd, whichis reproduced in Plate V. Some, taken in different stages ofthe Moon ’s libration, and therefore affording pictures such aswould be seen from different points of view, give an interestingappearance of solidity, and raise all the different formationsin picturesque relief when viewed in a stereoscope.* It may,however, be mentioned, that, when so directed, they also producean exaggerated elongation in the direction of that axis of theMoon which is pointed towards the observer.

It is to be hoped that lunar photography may be of con-siderable use, in enabling us, as time goes on, to test theoccurrence of any changes of surface, which, as we have pre-viously suggested, may arise from large slips or falls of land.Numerous photographs have also of late been most carefullymeasured by Professor Pritchard of Oxford, and by Dr.Hartwig of Strasburg, in order to determine the existence, oramount, of a slight physical libration or motion of the Moon ,about an axis of its figure, which theory tells us must exist.

The Moon , owing to the large amount of light received fromit, and its nearness to the Earth , is, with the exception of theSun, the easiest of all the heavenly bodies to photograph, *uidin some respects even more easy than the Sun, in consequenceof the overpowering amount of light which the latter affords.At the same time great care, a very well regulated instrument,and very refined processes are necessary to ensure success.Those, therefore, whose success has been so great as to bealmost perfect deserve all possible praise.

* Transparencies from the very beautiful negatives of Mr. De la Ruethus arranged may, we believe, be obtained from Messrs. Beck and Co.,Opticians, Cornhill, who have more than once very kindly lent some ofthem for the illustration of these lectures at Gresham College .

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