Lunar Perspective, 273 



variegated surface is brought more directly under the eye, 

 many objects become visible that could not be seen when, by 

 its proximity to the margin, it was greatly foreshortened. The 

 N. boundary presents a very different appearance, being both 

 curved and indented by numerous bays and valleys; indeed, 

 representations of this interesting region at the two extreme 

 epochs differ amazingly from each other. It is curious to 

 notice the remarkable and totally unexpected changes in form 

 that many spots present under these extreme conditions, and 

 when watched from night to night, and from season to season, 

 the gradations of change are highly interesting. As instances 

 we give two drawings of the well-known walled plain " Plato/'' 

 affected considerably by libration in latitude. 



The engravings represent the Lunar Crater Plato, as seen 

 under two different states of libration. The drawing of Fig. 3 



Fig. 3. 



was made in 1863, at Hartwell, on January 11, between 13 

 and 19 hours, Gr.M.T. The telescope used was the equatorial 

 of 5*9 inches aperture, powers 118 and 240. At the time the 

 drawing was made, Plato was under the evening illumination, 

 the moon having attained her greatest libration, the quadrant 

 in which the greatest change was observed being the S.E. At 

 this time the moon's latitude was about 4 o, 50' South, bringing 

 Plato nearer to the eye of the observer, so that the elliptic 

 form of the crater was widened, all objects being south and 

 west of their mean places. The prominent features in the 

 drawing are — 1st. The bright interior of the west wall of Plato. 

 2nd. The indented shadow of the east wall. 3rd. A formation 

 on the north of Plato, bounded on the west by a mountain 

 range. On the surface of this formation are two rills crossing 



VOL. XI. — NO. IV. t 



