228 



Abstracts of the Makerstoun Observations, 1843. 



cur at the same hour as the minimum or maximum of the monthly mean ; as these departures from the mean 

 are probably due to irregular disturbing causes, the following differences may be taken as some measure of 

 these disturbances in the different months of the year : — 



Monthly Means of Diurnal Ranges minus the Ranges of the Monthly Means of the Diurnal Variation : — 



Jan. 



Feb. 



Mar. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



0''74 



l'-74 



2'- 19 



l'-86 



r-07 



0'-99 



2'-35 



0'-95 



l'-92 



r-75 



r-22 



l'-90 



The difference is a minimum in January, it increases to a maximum in March, diminishes to a minimum 

 in June ; and, if we except the sudden increase in July, it again becomes a maximum in September. The means 

 of the differences for the four seasons are : — 



Winter ; January, November, December, mean 



Spring; February, March, April, 



Summer; May, Jxme, July, 



Autumn; August, September, October, 



1-29 

 1-93 

 1-47 

 1-54 



From this we are perhaps entitled to conclude, that a certain class of disturbances have their greatest 

 effect at the equinoxes, and their least effect at the solstices. 



Those disturbances which increase the diurnal range of the mean are evidently not included in this result. 



TABLE VII. — Means of the Diurnal Ranges of Magnetic Declination with reference to the Moon's 



Age and Declination for 1843. 











After Moon 





After Moon 





Moon's Age. 



Mean Range. 



Moon's Age. 



Mean Range. 



farthest 

 North. 



Mean Range. 



farthest 

 North. 



Mean Range. 



Day. 



/ 



Day. 



' 



Day. 



' 



Day. 



f 



15 



9-79 







9-92 







9-63 



14 



10-99 



16 



1017 



1 



8-55 



1 



13-01 



15 



8-67 



17 



10-95 



2 



8-25 



2 



12-96 



16 



8-71 



18 



903 



3 



12-15 



3 



12-71 



17 



9-20 



19 



9-70 



4 



9-60 



4 



13-61 



18 



8-44 



20 



9-23 



5 



10-28 



5 



11-11 



19 



9-30 



21 



9-57 



6 



12-31 



6 



10-37 



20 



9-98 



22 



8-95 



7 



15-52 



7 



8-90 



21 



9-37 



23 



9-22 



8 



11-40 



8 



8-35 



22 



9-91 



24 



9-25 



9 



8-45 



9 



9-03 



23 



10-12 



25 



11-15 



10 



10-74 



10 



9-42 



24 



13-21 



26 



10-57 



11 



980 



11 



9-64 



25 



10-98 



27 



11-89 



12 



11-16 



12 



9-35 



26 



9-70 



28 



11-21 



13 



9-97 



13 



10-92 



27 



9-88 



29 



10-56 



14 



9-23 











* 



This Table has been formed from Table VI. in the manner already described. Table II. 



i 



