Astronomical and Nautical Collections, 325 



for a fluxion," and the most convenient symbol will, perhaps, be u' ; 



asAM'= Ax ~ + ^- . ^- + . . . A.t a and d* a being writ- 

 da: 1.2 dx* 



ten for (Ax) 7 and (dx) 5 . 



P. 101. " Partial fluxions are often somewhat inaccurately ex- 

 pressed by a circuitous notation, in which the quantity supposed to 



dz 

 vary is set down both as a divisor and a multiplier ;" thus, — dx, if 



dx 



z = xt/, is understood to mean ydx, and not ydx + xdy : it was 



first proposed by Euler, who seems to have introduced the method, 



to distinguish a partial fluxion by enclosing it within a parenthesis, 



as ( — J dx ; and it is sometimes denoted by d^z ; but the addi- 

 tion of a comma to the d is a sufficient distinction to imply that 



— - is meant to signify the coefficient of that part of the fluxion of z, 

 dx 



which depends on the change of x only, without the verbal repetition 



of the remark that a partial fluxion is intended. 



vi. Occultations of the Planets and Fixed Stars not less than the 

 fourth magnitude j visible at Greenwich in the Year 1826, 

 By Thomas Henderson, Esq, 



January 31. $rti- Immersion at 16 h 59 m mean time. Difference 

 of declination 15', star south of moon's centre. Emersion at 

 17 h 36 m mean time. Difference of declination 11', star south. 

 Immersion takes place at 182° from moon's vertex towards the 

 east or left hand; and the emersion at 121° towards the west or 

 right hand. 



February 16. Saturn. Immersion at 3 h 8 m mean time. Diffe- 

 rence of declination 10'; Saturn south. Emersion at 3 h 52™ mean 

 time. Difference of declination 13'; Saturn south. Immersion 

 takes place at 175° from moon's vertex towards east, or left hand; 

 and emersion at 119° towards west, or right hand. 



February 20. 2a s. Immersion at 10 h 36 m mean time. Dif- 

 ference of declination 7'; star south. Emersion at ll fc 49 w , 

 mean time. Difference of declination 6' j star north. Immersion 



