506 
DR. Gr. NEUMA1EE ON THE LUNAR-DIURNAL VARIATION 
north curve ; the winter half-yearly south curve scarcely deserves the name of such, while 
the winter half-yearly north curve exhibits the oscillations in a far higher degree, 
although they are still somew T hat irregular. 
The doubt so often raised, whether during the winter season any lunar-diurnal 
variation was traceable at all, can, I think, not be entertained any longer, if we pay due 
attention to the facts which may be gleaned from our Table. Indeed we shall presently 
see, when speaking of the lunar-diurnal variation in the various years of observation, 
that in some cases the variation manifests itself in a very distinct manner even during 
those months when the sun’s declination is north. 
The principal features of the curves just enumerated may be delineated as follows: — 
Ad I. 1. The maximum value of the easterly deviation of the needle takes place at 
the time of the moon’s lower transit, and the minimum between 6 h and 7 h . A secondary 
maximum occurs at l h , and a corresponding minimum between 19 b and 20 h . The range 
of oscillation amounts to 24"-0. 
Ad I. 2. In this case the maximum seems to occur a little after the moon’s lower 
transit, and the minimum at 6 h , while a secondary maximum takes place at l h and a 
secondary minimum at 19 h , the greatest range amounting to 38"’69. 
Ad I. 3. I consider it most likely that in this instance two influences, counteracting 
each other in some measure, make themselves manifest, and it is therefore rather difficult 
to determine the extreme deviations so well as in the former cases ; but it appears that 
ll h and the hour between 7 h and 8 h are marked as extremes, in the first instance the 
easterly deviation reaching its greatest value, and in the latter the same occurring with 
respect to the westerly deviation of the needle. The greatest range amounts to 15' ,- 66. 
The nodes, where the three curves intersect each other, are at the hours 15 h -16 h , 
20 1 * 45 m , 3 h 20 m , and 8 h 40 m . 
Ad II. 1. The maximum of the east magnetic declination occurs at ll h , the minimum 
at 6 h , the greatest range amounting in this case to 22"*61. A secondary maximum takes 
place at l h , and a secondary minimum at 19 h . 
Ad II. 2. Primary maximum about 30 m past the superior passage of the moon, and 
the corresponding minimum at 6 h , with a range of 42"T7. Secondary maximum at 10 b , 
and minimum at 19 h . 
Ad II. 3. There is in this case scarcely any regularity in the oscillations of the needle 
observable, the extreme values differing by 14"-91. 
On account of the irregularity of the winter curve the nodes for this group are not 
well defined; they seem, however, to be between 14 h 30 m and 16 h 50 m , 20 h 50 m , 3 h 15 m , 
and 8 h 30 m . 
Ad III. 1. Maximum at 13 h and minimum at 7 h , giving a range of 33"’40 ; secondary 
extremes are noticeable at l h and 17 h . 
Ad III. 2. Maximum at 13 h , minimum at 17 h , greatest range 44"‘41 ; secondary 
maximum and minimum respectively at l h and 7 h . It is yet to be decided whether the 
deviation from the rule, that the minimum between the inferior and the superior pas- 
