( 266 ) 



of field. That field consists of forces touching concentric circles and 



1 



great -; — . 



sm r . - 



Postscript. Ill the formula for vector fields in hyperbolic spaces: 



Pot. X = Pl^ F, {r) dx + {-^%— F, (r) dx 



nothing for the moment results from the deduction but that to xy -Y 

 and \y X also must be counted the contributions furnished by infi- 

 nity. From the field property ensues, however, immediately that the 

 effect of these contributions disappears in finite, so that under the 

 integral sign we have but to read \^ X and \y X in finite. 



For the y/ at infinity pro surface-unity of the infinitely great 

 sphere is <^ order e~^'\ the potential-effect of this in finite becomes 

 <^ order re- («-2)'- X c^-'- z=r v^- ("-!)'•; so the force-effect <^ order 

 g— (n— i)r. gQ the force-effect of the entire infinitely great spherical 

 surface is infinitesimal. 



And the \y at infinity pro surface-unity is <[ order — ; it fur- 



1 

 nishes a potential-effect in finite < order e-^"-^'''. — , thus a force- 

 effect <i order e— («— D'-. — ; so the force-effect, caused by the infi- 



1 



nite, remains <i order — - . 



The reasoning does not hold for the force field of the hyperbolical 

 >S/^2 in the second interpretation (see under B § VIII), but it is in 

 the nature of that interpretation itself that the derivatives at infinity 

 are indicated as such, therefore also counted. 



Meteorology. — ''■On Magnetic Disturbances as recorded at Batavia." 

 By Dr. W. van Bemmelen. 



(Communicated in the meeiing of September 29, 1906). 



Some months ago Mr. Maunder of the Greenwich-Observatory 

 addressed a request to the Batavia Observatory to provide him with 

 a list of magnetic storms recorded at Batavia with a view of testing 

 his results as to the infiuence of the synodic rotation of the sun to 

 the occurrence of disturbances. 



Mr. Maunder concludes from an inspection of the disturbances 



