12 Mr J. D. Dana on the Volcanoes of the M ocn. 



altitudes of its mountains were first estimated by Galileo,* 

 and afterwards were mathematically calculated by Heveliust 

 and Riccioli. Sir William Herscliel continued the investi- 

 gations, and reported the probable activity of three of its vol- 

 canic mountains. J Mayer, Huth, Harding, and Schroter.§ 

 and more lately Gruithuisen and W. G. Lohrmann,|| are other 

 prominent names among those who have added largely to 

 our knowledge of the moon's surface. More recently still, 

 MM. Beer and Miidler have pursued this science of Seleno- 

 graphy with wonderful perseverance and labour, and have 

 given corrected results of all previous calculations, with mag- 

 nificent maps of the moon's topography .•[[ 1095 heights were 

 carefully measured by them, and their features, to a great 

 degree of accuracy, ascertained. These maps have afforded 

 M. Elie de Beaumont some deductions alleged as support- 

 ing certain geological theories. James Nasmyth, Esq., in 

 the Transactions of the Royal Astronomical Society for 

 the present year, has published important observations on 

 the features of the moon's mountains, and traced out their 

 volcanic character.** A very valuable memoir, on the 

 same topics, has been presented within the current year to 



* In the article referred to in the Annuaire des Longitudes, (p. 522), Arago 

 states that Clearchus, on the authority of Plutarch, described the moon as smooth 

 and lustrous like a mirror. Democritus attributed the spots to inequalities of 

 surface. Galileo first observed the lunar mountains with his telescope in 1610, 

 and estimated their height at one-twentieth of the diameter, giving 8800 metres 

 for their altitude, which but little exceeds their actual height. 



t J' Hevelius, Selenographia ; fol., Gedani, 1647. 



\ Phil. Trans, for 1780, p. 507, Astronomical Observations relating to the 

 Moon : — for 1787, p. 229, An Account of three Volcanoes in the Moon : — for 

 1794, p. 39, Account of some particulars observed during the late eclipse (in 

 1793) of the Sun. 



§ J. H. Schroter, Selenotopographische Fragmente zur genauren Kenntniss 

 der Mondflache ihcer erlittenen Veranderungen und Atmosphare ; 2 vols, 4to, 

 Gbttingen, 1791 and 1802. — Gruithuisen, in Bode's Astron. Jahrb., 1825. 

 . II Topographic der sichtbaren Mondobcrflache, von W. G. Lohrmann ; 4to, 

 Dresden und Leipzig, 1824. 



•[ Allgemeine vergleichende Selenographie ; mit besonderer Beziehung auf 

 die von den Vcrfassern herausgegebene Mappa selenographica, von W. Beer 

 und Dr J. G. Madler; Berlin, 1837. 



** Memoirs of tlie Ko} al Astronomical Society, vol. xv., 1846. On the Tele- 

 scopic Appeai-ance of the Moon, by James Nasmyth, Esq., p. 147. 



