=e 
Influence of the Moon on Declination of the Magnetic Needle. 99 - 
of treatment of the subject is that followed by os Sabine 
in his discussion of the results of the British observations. The 
details of the method will be better understood a an canes 
The time of the moon’s passage over the meridian of Phila- 
delphia (upper transit) was obtained from the American Alma- 
nac, the small correction for the difference of longitude being 
neglected. The observation nearest to the local mean svlar time 
of the moon’s —— was marked with a zero, signifying Oh of 
lunar time. The time of the inferior transit was next obtained, 
and the 2 oS nearest to it in time was waited 124, The 
greatest difference in interval between the moon’s transit and 
the time of observation could in no instance exceed half an hour. 
one nearest er oa between tie two consecutive lunar hours 
was omitted. 
The month of March, 1842, is aclieud as an example of work- 
ing the bi- -hourly series, and the tables are given in the complete 
paper which, it 1s expected, will be published in the Smithsonian 
Contributions to 
ne of the first. questions . oi determined is, how many of 
these residuals must be used to give a definite result, another one — 
‘that no undue constiny: errors influence the coat 
The results of the discussions of these three groups were also 
, on by Bessel’s parses ae treated by Pte meted ot 
ast squares, Two te formula suffice represent 
| Wh observations, and thee is no eonstant term, Se 
