Mr Pritchard on the Aberration of a Diamcynd Lens. 317 



having contributed to the extinction of this race of Gervi, is 

 one that is strictly geological. It is the gradual oblitera- 

 tion of the ancient pools and lakes, to the swampy banks of 

 which they originally resorted. Most of these, by dint of the 

 constant operation of atmospheric agents affecting the disinte- 

 gration of rocks, combined with other, yet subordinate, causes, 

 have, by the transported materials of rivers, been gradually 

 filled up, so as to at length present a surface well adapted to the 

 use and abode of man ; and when our Cervus was eventually 

 deprived of the covert of morasses and thickets, he became the 

 more easy prey of his natural enemies, whether of the human 

 race or of the lower animals. According to this view, then, 

 which I have amply illustrated in a former essay, the diminu- 

 tion or extinction of this very interesting race of Cervi has 

 kept pace with the obliteration of ancient lakes, and the 

 drainage of ancient marshes. 



I have at length concluded my history of the Certms eury- 

 ceros. But, as the validity of a favourite geological theory has 

 been involved in it, I would merely hint, that the object of the 

 present memoir was not to determine a question of this nature, 

 but one of zoological history. For the valuable services which 

 Dr Buckland has rendered to geological science, I continue to 

 entertain the same respect which I have always done ; and I 

 even agree with him, that illustrations of the Mosaic testimony 

 are to be expected from the study of the actual appearances 

 of nature. But with this general admission I would pause : — 

 the present essay will perhaps convey the information, that such 

 illustrations must be sought for amidst phenomena totally dif- 

 ferent from those, which geological commentators on the holy 

 writ have entangled in the articles of their creed. 



Art. XVIII. — Investigation of the Spherical Aberration of a 

 Diamond Lens. By Mr Andrew Pritchari), Hon. Mem. 

 Soc. Arts, Scot. &c. Communicated by C. R. Goring, M. D. 



As the superior distinctness and efficacy of a diamond lens 

 does not yet seem to be sufficiently appreciated by the public 



NEW SERIES, VOL. II. NO. II. APRIL 1830. X 



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