Meclimikal Philosophj. in 



IZack; and the successively improved lAiimr Tables 

 of Clair AULT, Euler, Mayef, Mason, and final- 

 ly, of BuRCKHARDT, foundcd on the observations of 

 Burg and Bouvard. Tables of all the primary 

 Planets, and their Secondaries, have been com- 

 pleted during the period in question; among the 

 ■most valuable of which are those of Bradley, 

 Cassini, De Lambre, WargentiNj Vidal, 

 Oriani, Schubert, Burckhardt, and De La- 

 lande. Tables of Parallax and Refraction have 

 been formed by Bradley, Dunthorne, and Shep- 

 herd, particularly the last, whose woTk is a won- 

 derful monument of industry and perseveranc€. 

 To these might be added a multitude of others, 

 published by individuals, and learned societies, va- 

 rious sets of which may be found in modern books 

 of astronomy. Those printed in De Lalande's 

 great systematic work, are probably exceeded by 

 none extant in fulness and accuracy. By means 

 of these Tables, many complex calculations, which, 

 without their aid, would cost the labour of several 

 hours, or even days, may now be performed in an 

 eighth or tenth part of the time which they for- 

 merly employed, and with much greater assurance 

 of a true result. 



Previous to the eio^hteenth centurv, thouofh 

 Eclipses, of various kmds, had been observed and 

 calculated, yet these operations had rarely been 

 made subservient to any important practical pur- 

 pose. Within a few years past, philosophers have 

 paid more attention to this part of astronomy. 

 Methods have been devised of calculating eclipses 

 wuth more ease and expedition than before. Large 

 collections of these calculations have been made, 

 for a long series of years, with the view of de- 

 ducing from thence the longitude of cities, and 

 determining other astronomical and geographical 

 questions. Among those who have distinguished 



