386 



Results of Makekstoun Obseevatioxs, 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 

 fi-om the Earth, for 1844. 



This Table has been formed fi-om 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 : — 



29 days to 1 day. New Moon, 



2 5 days, 



6 9 



10 13 



Mic. Div. 



17-3 

 13-4 



18-5 

 240 



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 pomts 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 gi-eatest north and soutli 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 

 204 

 17'6 

 15-8 



Mic. Div. 



13 days to 15 days, Moon farthest South,... 16-2 



16 19 20-6 



20 22 18-1 



23 26 22-0 



south 



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



