462 Nautical Ephemeris. 



continued in the general explanation prefixed to the Almanac. At 

 no time were these observations likely to be of more essential ser- 

 vice than at the present. From the various anonialies which have 

 occurred in the course of the great Trigonometrical Survey, it ap- 

 pears that the latitudes and longitudes of places, determined as- 

 tronomically, can no longer be considered as accurate expressions 

 to designate the relative situation of places on the earth. These 

 anomalies are supposed to arise either from irregularities in the 

 figure of the earth itself, or from certain irregularities in the den- 

 sity of its strata, causing a deflection of the plumi)-line from the 

 position it would otherwise assume. In either case a careful com- 

 parison of the latitudes and longitudes of different places deter- 

 mined trigonometrically, with those of the same places derived 

 from astronomical observations, seems to be the only probable 

 way of throwing light on this intricate subject, and leading us to 

 a true knowledge of the earth's figure, 



There is, perhaps, no method of determining the longitude 

 astronomically with greater accuracy, than from the occultations 

 of the fixed stars by the mooH. They are also of frequent oc- 

 currence ; and as there are many individuals iii this coimtry who 

 possess the means of making these observations with accuracy, 

 one would wish that every assistance should be afforded that 

 might invite to it. Until our Astronomer Royal shall again af>» 

 ford this, perhaps the insertion in your Magazine of such astro- 

 nomical phaenomena as will occur during the month may not be 

 unacceptable to your readers : if you think so, the inclosed (for 

 January 1817) are at your service, and shall be followed by 

 pthers in due time. 



I am, sir, your obedient, &;c. 



* * * 



Astronomical Pkcenomena, January 1817. 



B. H. M. D. H. M. 



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