1826.] Telescopicai Observations on the Moon, 435 



time before the micrometer need be used. The figure here given 



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tSarmaCice 

 JPars. -- 



is the result of a considerable number of observations. I first 

 obtained a view of the most prominent parts with my short 

 aerial, using a power of about 60. A similar view to what I 

 then obtained is given in Hevelius's Map, entitled, "Tabula 

 Selenographica Phasium Generalis," (Selenographia, p. 202). 

 The different views obtained at various ages of the moon are to 

 be found in Maps Nos. 8 to 20, in some of which, parts of the 

 broad line which runs almost parallel to the margin of Moeotis 

 are most conspicuous ; in others, some of the lines which con- 

 nect it with Moeotis are seen. In Cassini's Map, given in 

 Smith's Optics (the only representation given by that astronomer 

 which I possess), similar portions are to be seen. 



On applying my reflector with powers of 130 to 400, the 

 appearance is as in the figure. A scientific friend of mine lately 

 observed a part of what is here delineated with an excellent five 

 foot achromatic ; but having less power and light than my 

 reflector, he did not see the finer lines ; and from occasional 

 glimpses I have had, I have not been able to trace them to their 

 full extent, although, on one occasion, I used a power of 800, 

 which is very distinct, and has abundance of light. To see the 

 appearances, the air should be in such a state that good and 

 steady discs of the stars may be obtained ; the telescope must 

 have abundance of light, a high power, and be very steadily- 

 mounted. Under these circumstances, it frequently happens. 



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