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Astromony. — "On the astronomical refractions corresponding to 

 a distribution of the temperature in the atmosphere derived 

 from balloon ascents" Preliminary paper by H. (*. van de 

 Sandk Bakhuyzkn. 



J. The various theories of the astronomical refraction in our 

 atmosphere consider the atmosphere as composed of an infinite 

 number of concentric spherical strata, each of uniform density, whose 

 centre is the centre of the earth and whose densities or temperatures 

 and refractive powers vary in a definite way. 



The various relations between the temperature of the air and the 

 height above the surface of the earth, assumed in the existing- theories, 

 are chosen so, that 1 st they do not deviate too far from the suppo- 

 sitions on the distribution of the temperature in our atmosphere, 

 made at the time when the theory was established, 2 nd that the 

 formula derived from this relation for the refraction in an infini- 

 tesimal thin layer at any altitude could be easily integrated. 



At the time when the various theories were developed, only little 

 was known about the variations of the temperature for increasing 

 heights, and this little was derived from the results of a small 

 number of balloon ascents and from the observations at a few mountain- 

 slat ions. In the last decade, however, ascents of manned as well as 

 of unmanned balloons with self-registering instruments have greatly 

 increased in number, and our knowledge of the distribution of the 

 atmospheric temperature has widened considerably, and has become 

 much more accurate. Now I wish to investigate, whether by means 

 of the data obtained, we can derive a better theory of refraction, or 

 if it will be possible to correct the results of the existing theories. 



2. The temperatures in our atmosphere at different heights have 

 been derived from the following publications : 



I. Ergebnisse der Arbeiten am aëronautischen Observatorium Tegel 

 1900—1902, Band I, II and III. 



II. Travaux de la station Franco-scandinave de sondages aëriens a 

 Halde par Teisserenc de Bord. 1902—1903. 



III. Veröffentlichungen der internationalen Kommission für wissen- 

 schaftliche Luftschifffahrt. 



From the last work I have only used the observations from 

 December 1900 till the end of 1903. 



I wished to investigate the distribution of the temperature up to 

 the greatest heights, and therefore 1 used for my researches only 

 the balloon ascents which reached at least an elevation of 5000 meters; 



