PART I. ON MAGNETIC STORMS. CHAP. III. 



TABLE XXVI. 



173 



well-defined perturbation, occurring almost exclusively in D and V, and having a course similar to that 

 of the already-mentioned perturbation which occurs at Sitka during this period. 



Neither at Dyrafjord nor Matotchkin Schar is any perturbation with a course such as this to be 

 observed between 13** 45"* and I5 h 35. 



At Tiflis a peculiarity appears, in that the maximum occurs much earlier than in Central Europe; 

 and when the maximum is reached there, there is nothing of that kind at Tiflis, or at any rate only a 

 small secondary. At the time that the powerful perturbation in D commences in Central Europe, the 

 declination conditions at Tiflis are undergoing no particular change. The //-curve, on the other hand, 

 forms a bend similar to that appearing in D farther north; but this deflection is in the opposite direction 

 to that before and after it, its only effect being to cause the perturbing force to become smaller and 

 make an oscillation. 



At Dehra Dun, Bombay and Batavia also, the //-curve is about of the same form, the only differ- 

 ence being that this deflection in an opposite direction is so prominent that the total force PI, becomes 

 greater than that with the previously reverse direction, and the maximum comes at the given place after all. 



The conditions are probably most likely to be understood as follows. While the perturbation in 

 Central Europe is great in D, we are concerned with the effect of at least two simultaneously acting, 

 principal systems. One of the perturbations is of long duration, and in low latitudes the form of its field 

 remains fairly constant. While it is going on, a comparatively poverful storm commences, with a some- 

 what different distribution of force. 



