Aslronotnical and Nautical Collectio7is. 347 



of observation, which being compared with the time of the same 

 phenomenon for Greenwich, as given in the Ephemeris, the longi- 

 tude of the place from Greenwich will be obtained. 



Example: — Nearest distance . . + 50 31 

 Perpendicular Par. . . — 39 57 



Sum + 10 34 



Semidiameter . . . 14 46 



Sum 25 20 P. L. 8516 



Difference .... 4 12 P. L. 1.6320 



2)2.4836 



Side + 10 19 1.24T8 



Orbital Par - 24 56 



- 14 37 



The space 14' 37", reduced into time, at the rate of 29' 42" for 

 an hour, gives us 29'" 32' to be subtracted from o^ 46_^ 50% the 

 time of the immersion, and makes 3** 17"" IS' for that of the near- 

 est approach, differing 17' from the solar time at Greenwich. 



iv. Error in a Table of Logarithms. 

 In tables that are to be used without time for consideration, the 

 slightest errors deserve to be made generally known. The number 

 8814 is printed 6814 in Lalande's pocket tables, edition revue 

 par M. Regnaud, Paris, 1818. 



V. Historical Sketch of the various Solutions of the Problem of 

 Atmospherical Refraction, from the time of Dr. Brook 

 Taylor, to that of the latest computations. 



In justice to the claims of departed merit, it is often necessary to re- 

 vert to the first steps by which the inventions of modern mathemati- 

 cians have been prcpared,if not anticipated : but it seldom happens 

 that the earlier solutions of a problem have been so completely 

 forgotten as appears to be the case with the investigations of 

 Dr. Brook Taylor respecting the path of light in the earth's atmo- 



2 A 2 



