386 



Results or Makerstoun Observations, 1844. 



TABLE LI. — Mean Difference of a Single Observation of the Balance Magnetometer from the Monthly 

 Mean, at the corresponding hour, with reference to the Moon's Age, Declination, and Distance 

 from the Earth, for 1844. 











After 





After 





Before 





Before 





Moon's 



Mean 



Moon's 



Mean 



Moon 



Mean 



Moon 



Mean 



and 



Mean 



and 



Mean 



Age. 



Difference. 



Age. 



Difference. 



farthest 

 North. 



Difference. 



farthest 

 North. 



Difference. 



after 

 Perigee. 



Difference. 



after 

 Apogee. 



Difference. 



Day. 



Mic. Div. 



Day. 



Mic. DiT. 



Day. 



Mic. Dir. 



Day. 



Mic. Div. 



Day. 



Mic. Div. 



Day. 



Mic. Div. 



15 



18-9 







220 







16-8 



14 



16-7 



7 



17-3 



7 



20-4 



16 



21-8 



1 



15-5 



1 



15-3 



15 



161 



6 



15-3 



6 



17-2 



17 



24-9 



2 



13-3 



2 



18-7 



16 



17-1 



5 



27-4 



5 



22-9 



18 



21-3 



3 



12-6 



3 



16-7 



17 



220 



4 



18-2 



4 



14-4 



19 



27-7 



4 



12-7 



4 



210 



18 



19-8 



3 



160 



3 



18-9 



20 



17-8 



5 



15-2 



5 



25-3 



19 



23-6 



2 



15-6 



2 



29-7 



21 



16-6 



6 



24-6 



6 



18-5 



20 



18-5 



1 



20-2 



1 



18-1 



22 



15-7 



7 



14-8 



7 



15-6 



21 



20-0 



P 



17-2 



A 



22- 1 



23 



15-7 



8 



16-4 



8 



18-6 



22 



15-9 



1 



16-7 



1 



14-8 



24 



14-3 



9 



18-3 



9 



16-8 



23 



25-0 



2 



17-9 



2 



16-5 



25 



16-2 



10 



24-9 



10 



15-2 



24 



22-8 



3 



15-3 



3 



14-4 



26 



12-9 



11 



17-5 



11 



14-2 



25 



17-6 



4 



16-7 



4 



160 



27 



16-1 



12 



29-9 



12 



17-2 



26 



22-6 



5 



24-5 



5 



16-5 



28 



15-4 



13 



23-6 



13 



15-9 



27 



191 



6 



18-4 



6 



17-7 



29 



14-4 



14 



25-0 











7 



19-9 



7 



200 



This Table has been formed from Table L., in the manner already described for Table II. 



Variation of the Mean Difference with respect to the Moon's Age. — From the first portion of Table LI., 

 it appears that the mean difference is a maximum about opposition, and a minimum about conjunction. The 

 following are means of groups : — 



Mic. Div. 



14 days to 16 days, Full Moon, 21-9 



17 20 22-9 



21 24 15-6 



25 28 15-1 



Mic. Div. 



29 days to 1 day, New Moon 17-3 



2 5 days, 13-4 



6 9 18-5 



10 13 24-0 



The law is the same as that already found for the horizontal component ; there is a secondary maximum 

 at conjunction, minima occurring immediately before and after it ; and there is a secondary minimum at oppo- 

 sition, the maxima occurring immediately before and after it : these secondary points are perhaps accidental. 



The average difference for the 11 days (10 — 20), including Full Moon, . =23-0 Mic. Div. 

 (25 — 5), New Moon, . =151 



Variation of the Mean Difference with reference to the Moon's Declination. — The average difference is a 

 minimum when the moon has its greatest north and south declination, and it is a maximum between these 

 epochs when the moon is near the equator. The following are means of groups : — 





27 days to 1 day, Moon farthest North, 



2 5 days, 



6 8 



9 12 



Mic. Div. 



. 17-1 



20-4 



17-6 



15-8 



13 days to 15 days, Moon farthest South, 



16 19 



20 22 



23 26 



Mic. Div. 



. 16-2 

 20-6 

 181 

 22-0 



south. 



These means still present some irregularities ; the principal minimum occurs when the moon is farthest 



