Correspondence. 91 



Sunday's River Valleys, and on the overlying recent rocks especially, 

 many years ago, long before the subject had attracted much attention 

 from European Geologists, and I brought forward in a letter to Sir 

 Charles Lyell most of the facts here given. — Yours truly, 



E. N. EUBIDGB. 

 Poet Elizabsth, South Apkica. 



ON THE GLACIAL CONDITION OF THE MOON'S SURFACE. 

 To the Editor of the Geological Magazine. 



Sir, — AUow me to send you the following results of some re- 

 searches into the surface of the Moon. Viewed by the naked eye, 

 the colour of the lunar disk is uniform, ojr nearly so, presenting to 

 the spectator at night a disk or mirror of light, reddish-yellow when 

 seen near the horizon, and in a hazy atmosphere, but of a much paler 

 yellow, or almost white, when seen high up in the horizon under a 

 clear atmosphere ; and on a bright day, and in a blue sky, as white, 

 or whiter, than the fleecy clouds which float past it. Seen with a 

 telescope, the Moon loses much of its yellow appearance, which is 

 due to our atmosphere, and has an apparent liquid electrum colour, 

 still uniform, but revealing the mountains, Avith their apparent 

 craters, and shadowy and dark patches, or non-reflecting surfaces. 

 Neither of these visual observations are sufficient as yet to determine 

 the nature of the surface ; and, although the most powerful instru- 

 ments bring it within 240 miles of the eye of the astronomer, even 

 that distance does not seem sufficient to deprive the disk of its 

 reflecting power, so as to enable the observer to distinguish the 

 relative colours of which its surface is composed. Now, an inspection 

 of the photographic and stereoscopic views of the Moon offer what I 

 consider as a revelation of its condition, and demonstrate it to be 

 completely Glacial. Of this I am firmly convinced, from a minute 

 and careful examination of the lUnar stereograph of Mr. H. De la Rue, 

 and a careful comparison with a great number of Alpine photographs 

 and stereographs in the possession of Mr. F. E. Blackstone. For 

 not only does the former exhibit unequivocal proof of being taken 

 from an object of which the dominant colour is white, but the surface 

 exhibits all the peculiar transparency in textures of Snow, Ice, and 

 Glaciers, seen in the latter. I cannot be deceived on that point, 

 and I feel the more confident, since a great portion of my time 

 has been spent in the examination of surfaces. 



Now, although the stereoscope does not supersede the actual 

 observation by the eye, it is a powerful aid to the determina- 

 tion of this question. The stereograph of Mr. De la Rue is 2| in. 

 diameter, and gives 2,161 miles of the Moon's diameter, offering 

 to the eye an optical model of the luminary about the size of a 

 billiard ball, on which all the elevations of the mountains appear 

 in relief. When looked at attentively, all the luminous parts of the 

 Moon present the appearance of a Glacial country such as the wintry 

 Alps or the Polar regions. Portions of it aj)pear as extensive plains 

 and ranges of elevated ground covered with snow and ice, while 



