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for building an observatory, I suggested to Government the 

 idea of renting a house at Batavia and adapting this to a 

 temporary observatory. I succeeded in obtainiug a house 

 extremely well situated for the purpose, in which I could 

 commence, on Jauuary 1-"^ 1866, hourly meteorological and 

 magnetical observations with a staff of Javanese assistants 

 who had been trained by myself to good observers and 

 computers. The system of hourly observations, I then be- 

 gan, has been continued without interruption duriug thir- 

 teen years. 



In 1871 I published a volume containing the observations 

 made at the temporary observatory in the years 1866, 1867 

 and 1868. Now I present to the public two other volu- 

 mes containing the observations made from 1869 to 1875. 

 Next year I hope to publish the last three years of obser- 

 vations made on the system introduced at the temporary 

 observatory. This system will be replaced in 1879 by that 

 of the newly built observatory, principally based on the use 

 of photographically and other self-recording Instruments and 

 which I have no doubt will prove far superior to the old 

 system, especially for magnetical observations. 



The principle on which the Batavia Observatory was to 

 be organized, being still a matter of discussion for Govern- 

 ment when I published my first volume of observations, I 

 thought it better then not to enter into any details concern- 

 ing it. Now, however, the question having been decided, 

 and the Observatory having been built, I feel at liberty to 

 say a few words about its history. At the same time I 

 wish to fulfil now a duty which I have been obliged to 

 defer too long, the duty of expressing my most hearty thanks 

 to all those who have assisted in any way in the founda- 

 tion of the Batavia Observatory : — to the Royal Academy 

 of Sciences at Amsterdam, who so efiectually supported 

 VoN Hümboldt's suggestion; to Professor Buys Ballot, the 

 Director of the Royal Dutch Meteorological Institute at 

 Utrecht, who first made a detailed plan to give execution 



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