( 77G ) 



tbr a number of cases, in wliicli thai movement had made its ai)peai'- 

 ance under difïerent circumstances at IJatavia. The answers were of 

 a very different nature and therefore I made of eacii case a summary 

 diagram in whicli in an equal manner under eadi otiier was noted 

 down the registration image of //, D and Z for each station. In 

 many respects it wouhl be useful to reproduce these diagrams, but 

 the difficulties connected witli it and the numerous imperfections of 

 the material have made me set it aside. 



These imperfections are cliietly (caused by the measure of time of 

 the diagrams of the various observatories not being taken ample 

 enough to be able to lix the simultaneity of the different movements, 

 which take place within a few minutes. 



From the notation of the Töpfer-Schulzk magnetograph at Buiten- 

 zorg where the circumstances were pretty favourable I could deduce 

 with certainty that the commencement of the movement of the three 

 components is often not simidtaneous. Accuracy down to parts of 

 minutes cannot be demanded of most magnetic diagrams, where 1 

 hour takes up 10, 15 or 20 mm. It was therefore impossible to draw 

 trustworthy maps, on which the vector of disturl)ance during the 

 initial movement was represented in its varying magnitude and 

 direction, so I must restrict myself to the following. 



In the following table the direction of the movement has been 

 given for all the cases. 



In the case of an introductory movement of slight amplitude this 

 is indicated for H by +/— or — /+, for D by wjE or el W. 



In some cases the introductory movement was of the same order 

 of amplitude with the following movement and this is accordingly 

 indicated by +/— or — /+ and WiE or ElW. 



We see in this table the movements of one or more elements for 

 different constant direction. Further information is furnished by the 

 annotation of the Rev. P. de Moidkky in the "Bulletin des Observations 

 de 1' Observatoire de Zie-Ka-Wei, T. XXXI" and the copies of 

 disturbances for Greenwich, Pare st. Maur and Samoa. The former 

 states for Zi-Ka-Wei the freipiency of the positive H and Z 

 movement at 95 pCt. and of the E movement of D at 90 pCt. ; 

 whilst out of the Samoa curves the H and Z movement proves to 

 be -f- in 9 cases. 



