687 



CONTENTS. 



PAGE 



Table I. Positions of the Principal Observatories. From the At7ierican, 



English, and German Nautical Almanacs .... 5 



" II. To convert Parts of the Equator in Arc into Sidereal Time, or to 

 convert Terrestrial Longitude in Arc into Time. From Downes, 

 U. S. Almanac for 1845, as given in Lee's Tables and Formulae, 

 2d edition, p. 14G et seq. ....... 9 



" III. To convert Sidereal Time into l-'arts of the Equator in Arc, or to 

 convert time into Terrestrial Longitude in Arc. From Downes, 

 U. S. Almanac for 1845, p. 150, and Lee's Tables and Formulae 11 



" IV. For converting Sidereal Time into Mean Solar Time, and Mean 

 Solar Time into Sidereal Time. From Lee's Tables and 

 Formulae . . . . . . . . . .12 



" V. Correction of the Time obtained by Observation of the Sun, in 

 order to have the True Time of the Clock. Communicated by 

 Prof. B. Peirce, of Harvard University . . . .13 



" VI. Tables giving the length of a Degree of the Meridian and of the 



Parallel, calculated according to the formula of Clarke . . 14 



'' VII. For computing Terrestrial Surfaces, based on the preceding Tables 19 



1) Quadrilateral surfaces of 1 degree .... 20 



2) " " " 2 degrees . ." . .22 



3) " u <« ,5 u .... 23 



4) " " " 10 " .... 23 



5) " " " 1, 10, 20, and 30 minutes . 24 

 " VIII. Comparison of the Standards of Length of England, France, 



Belgium, Prussia, Russia, India, and Australia ... 25 

 *' IX. Table giving tiie length of Insolation for any given Latitude . 27 



c 



