364 SPECIAL RESULTS IN THE URANOLOGICA.L 



between the bright and dark parts of the Moon, of the 

 illuminated mountain summits appearing as points of light 

 on the dark part, or by the length of the shadows. The 

 first method was that employed by Galileo, as is evident 

 from his letter to Pater Grienberger on the Montuosita della 

 Luna. 



According to Madler's careful determinations made 

 by measuring the lengths of the shadows, the culminating 

 points of the Moon near the southern margin, very near 

 to the pole, are, in descending series Dorfel and Leib- 

 nitz, 3800 toises (24300 English feet); the annular moun- 

 tain, Newton, where a part of the deep excavation is never 

 shone upon either by the light of the Sun or that of the 

 Earth, 3569 toises (22822 Eng. feet) ; Casatus, east of 

 Newton, 3569 toises (22822 Eng. feet) ; Calippus, in the 

 Caucasus chain, 3190 toises (20400 Eng. feet) ; and the 

 Apennines between 2800 and 3000 toises (17900 and 

 19180 Eng. feet). It must here be remarked, that, from 

 the total want of a general zero line of level (a plane equi- 

 distant from the centre of the body, like the surface of the 

 sea in our own planet), the absolute heights are not strictly 

 mtercomparable : the six numerical results given above 

 express, properly speaking, only tlie differences between the 

 summits and the nearest plains or low points ( 387 ). It is 

 -certainly a striking circumstance that Galileo attributed to 

 the highest mountains in the Moon an elevation of " incirca 

 miglia quatro" about four geographical miles of 60 to 

 the terrestrial equatorial degree, or 3800 toises, the height ac- 

 tually assigned above to the lunar mountains Dorfel and 

 Leibnitz. According to the hypsometric knowkdge possessed 

 by him, Galileo estimated this height as superior to that of 

 any terrestrial mountain. 



