350 Results of the Makerstoun Observations, 1844, 



Diurnal Variation of the Positive and Negative sums of Disturbances. — Tlie following are the sums for 

 each hour in 1844 : — 



12' l^A.M. a"- 3'i i'' 5'' ei" "'■ S'> 9h 10'' ll'' 01' 1'' P.M. 2'' 3'' 41' 5'' 6'' T' S'' 9'' lO"" 11'' 

 + 156' 178' 225' 240' 244' 294' 345' 355' 391' 455' 413' 375' 408' 361' 363' 329' 280' 222' 182' 151' 107' 110' 117' 105' 

 - 446 413 322 264 266 201 127 118 92 87 87 103 97 102 126 183 184 233 415 416 593 487 484 549 



These values, when projected, produce two curves of remarkable regularity. The sum of the positive 

 disturbance is a minimum about IC'p.m. ; it increases regularly from thence till about G*" 10™ a.m. ; the 

 intei-polated maximum occurs about 10'' a.m.; it then diminishes, after noon, with the previous regularity, till 

 about 8'' P.M. Tlie sura of the negative disturbance, on the contrai-y, is a maximum about 10'' p.m., and it 

 Incomes a minimum about 10'' a.m.; tlie range of the positive sums is about a tenth less than the range of the 

 negative sums. Each of the two curves is irregular once in the 24 hours, and, curiously enough, this does 

 not occur at the same time; the negative disturbance curve is irregxdar from 8'' p.m. till 11'' p.m., while the 

 positive disturbance curve has nearly constant ordinates. On the contrary, the positive disturbance curve is 

 irregular from about 9'' a.m. till 1'' p.m., wliile the regularity of the negative curve is most marked. The 

 characteristics of these curves are therefore identical, when we consider the ordinates at 12 hours' interval. 

 It is obvious, then, that we have in the positive disturbance curve a simultaneous representative of the negative 

 disturbance curve for our periaeci, the sign of motion with reference to space, or the sun, being the same for both. 



The result obtained for the year is also shewn, with considerable regularity, in the sums for each month. 

 In the discussion of the total sums of dift'erences, it appeared that the epochs of maximum and minimum 

 varied with season. A consideration of the positive and negative portions, renders it probable that this variation 

 is accidental ; thus, thougli the minimum of the total sums of differences occurred, for the summer quarter, at 

 5'' or 6'' p.m., the positive disturbance has its maximum, for the same quarter, about 10'' a..m., and its minimum 

 about 10'' p.m., the reverse being true of the negative disturbance, which is exactly the law of the sums from 

 the whole observations of the year. 



Annual Variation of the number of Positive Disturbances. — Tlic following are the numbers per cent, of 

 hourly observations in each month, which were positive, or to the west of the normal mean : — 



Oct. Nov. Dec. 



47-2 .580 60-4 



Taking the mean for cacli three months as the mean for the middle month — 



.55-7 55-5 54-9 53-5 50-9 49-6 49o 50-3 50-9 53-3 .55-2 56-6 



From wliich it would appear, that the number of excursions to the west of the normal mean is a maximum 

 at the winter solstice, and a minimum at the summer solstice. The reverse holds for the excursions to the 

 east of the normal mean. In the year 1844, thei-e were in 100 hourly observations of magnetic declination, 

 53 to the west and 47 to the east of the normal means. 



Diurnal Variation of the number of Positive Disturbances. — The numbers per cent, for each hour, in 1844, 

 which are to the west of their normal means, are — 



laii 111 .4.M. 21' S' 41' 31' 61' 7'' S' gi- 101' lib 01' l' P.M. 2i> 3' 4' 5' 61" 7i' 8'' 9^ lO' lli- 

 38-5 39-2 47-5 "iO-fl 44-3 50-6 57'0 58-9 64-3 69-1 66-6 64-6 69-7 653 62-1 59-6 58-3 51-9 48-4 47-1 382 41-7 38-2 39-2 



The number is a maximum at about 11'' a.m., and a minimum about 10^'' p.m. There are twice as many 

 excursions to the west of the normal mean at 10'' a.m., as there are to tlie east, and there are about three 

 excursions to the east for two to tlie west at 10'' p.m. 



Diurnal Variation of the Positive and Negative Means of Disturbance. — Since the number of positive 

 disturbances is greatest when the sums of their excursions are greatest, and least when the sums are least, it is 

 still unknown whether the increase of the sums is solely due to the increase of the number of disturbances, or 

 whether the average positive or neg.itive excursion increases with tlie number. The following are the average 

 positive and negative excursions for each hour, together with the average of all the disturbances, without 

 respect to sign : — 



12" I'a.m. 21' 31> 4'' 51" 6li 71' 31' 91' lOl" 111' i)'' ll'p.M. 2l' 3'' i" S" (il> 71' 8'' 3l' lOl' U'' 



+ 1-29 1M& 1-51 1'53 1-75 1-85 1-93 1*92 1-93 2*10 1-97 1.85 1'8C 1-76 1*86 r76 1-53 1'36 1-20 1-02 0'89 0-84 0-98 0-85 



-2'31 2-16 1-95 1-68 I'52 1;10 0'94 0'9I 0'82 0'90 0'82 0-92 I'02 0-94 1-06 1'44 1'41 1-S4 2'56 2'50 3-U7 2-66 200 287 



All. I'»J 1-88 1'74 fOO 1 02 1-58 1-50 1-50 1'54 1-73 1-59 1-52 1-60 1-48 1-56 1-C3 1'48 1-4S 1-90 1-81 2'28 1-90 1-92 2-08 



