The value of the coefficient of terrestrial refraction K has been determined with the help of zenith distance measurements carried out between two observing stations situated at a distance of 15122,55 m and absolute heights equal to about 177 m and 361 m in the area of Thessaloniki. A total of 1924 hourly values of K covering 128 days during the years 1969-1974 have been thus obtained. On the basis of this material the variation of the value of K during each day and from day to day, as compared with the corresponding variation of air temperature has been studied. In the second part of the paper a method for the determination of the vertical temperature gradient c with the help of the coefficient of terrestrial refraction is described. With the help of this method 1924 values of c for the area under consideration have been determined. On the basis of this material the variation of the value of c during each day and from day to day as compared with the corresponding variation of air temperature has been studied.
Μελετώνται οι θεμελιώδεις σχέσεις σχετικά με τη γεωδαιτική διάθλαση, παρουσιάζονται οι μετρήσεις οι οποίες έγιναν, μελετάται η μεταβολή του συντελεστού γεωδαιτικής διαθλάσεως συναρτήσει του χρόνου, ο προσδιορισμός της τιμής της κατακορύφου θερμοβαθμίδος από τον συντελεστή γεωδαιτικής διαθλάσεως και η μεταβολή αυτής μετά του χρόνου και τέλος οι θεωρητικές τιμές του συντελεστού γεωδαιτικής διαθλάσεως.
