184 



Proceedings of the Royal Irish Academy. 



of tlie eclipse, and in subdividing it into intervals of hours and minutes. 

 Lastly, from the latitude-parallax-scale is taken an extent equal ta 

 the sum of the semi-diameters reduced of the sun and moon, and one 

 foot being set on the moon's path and the other on the path of the 

 observer, the compasses are moved backwards and forwards till the 

 points fall into the same hour and minute in both paths, thus showing 

 the required times. 



To facilitate the subdivision of the latitude-parallax-scale, and of 

 the hours on the moon's path, two diagrams may be dra-v\Ti as on 

 page 185, only enlarged in magnitude : — 



The moon's horary motion in right ascension is taken from the 

 "variations for lO""," given in the Nautical Almariac, by calling the 

 seconds of time minutes of arc, and increasing these quantities half as 

 much again. The moon's horary motion in declination is taken from 

 the corresponding quantities in the same page, by regarding the 

 seconds of arc as minutes of arc, and dividing by 10. 



Taele of Values of Ten Divisions of the Latitude-Parallax- Scale, and of 

 Pp sin I, for Greenwich Lat. Geoc. 57° 17' ]^., used in construction 

 of Occultations and Eclipses. 



Horizontal 

 Parallax. 



Value of 

 Ten Divis. 



t > 



5 li 



>. 



o 

 o 



s 





"^ c 



Difference. 

 Pp sin / X 



o 



c 



c 



53' 



302-4 



1-2 41' 



28 



•15 



58'-0 



276-3 



1-0 45' 



17 



16 





2 



301-2 





1 



43 



•16 



•2 



275-3 



•9 



33 



15 





4 



3001 





1 



59 



•16 i 



•4 



274-4 



1-0 



48 



16 





6 



299-0 





1 



75 



•16 1 



•6 



273-4 



•9 



64 



15 





8 



297-9 





2 



91 



•15 



•8 



272-5 



•9 



79 



16 



54' 







296-7 





1 42' 



06 



•15 



59'-0 



271-6 



1-0 



95 



15 





2 



290-6 









21 



•16 1 



•2 



270-6 



•8 46' 



10 



16 





4 



294-6 





1 



37 



•15 



•4 



269-8 



•9 



26 



15 





6 



293-5 





1 



52 



•16 



•6 



268-9 



•9 



41 



16 





8 



292-4 





1 



68 



•15 ; 



•8 



268-0 



•9 



57 



16 



55' 







291-3 









83 



•16 



60' -0 



267-1 



•9 



73 



15 





2 



290-3 





1 



99 



•16 



•2 



266-2 



•9 



88 



16 





4 



289-2 





43' 



15 



•15 1 



•4 



265-3 



•9 47' 



04 



15 





6 



288-2 









30 



•16 



•6 



264-4 



-8 



19 



16 





8 



287-2 





1 



46 



•15 



•8 



263-6 



•9 



35 



16 



56' 







286-1 









61 



•16 



61'-0 



262-7 



•9 



51 



15 





2 



285-1 









77 



•15 



•2 



261-8 



•8 



66 



16 





4 



284-1 









92 



•16 i 



•4 



261-0 



•9 



82 



15 





6 



283-1 





44' 



08 



•16 ! 



•6 



260-1 



-8 



97 



16 





8 



282-1 









24 



•15 : 



•8 



259-3 



■8 48' 



13 





57' 







281-1 









39 



•16 















2 



4 



280-1 

 279-2 





9 

 



55 

 70 



•15 

 •16 









X CO 



sS. 





6 



278-2 









86 



•15 















8 



277-2 



■9 45' 



01 















58'-0 



276-3 



•10 



•17 



X 



cosS. 













