at the Magnetic Observatory at Prague. 421 



1839. July. Horizontal intensity = 532-41 



August. = 465-54 



September. = 488-85 



October. = 489-12 



November. - = 559-27 



December. = 598-58 



1840. January. = 586'91 



February. = 552-68 



March. = 560-01 



April. = 498-00 



May. = 437-17 



June. = 396-01 



The numbers here given are not corrected for the influence 

 of temperature, because it appears to affect not only the in- 

 tensity, but also the direction of the magnetic force, and we 

 must wait for more certain data. The continued and simul- 

 taneous observations of the bifilar magnetometer and the in- 

 clinatorium have shown, indeed, that changes of temperature 

 are always accompanied by changes in the horizontal intensity; 

 but they are also accompanied by corresponding alterations 

 in the dip, which increases as the horizontal intensity de- 

 creases, and vice versa. 



In some months of the year a decrease takes place in the 

 horizontal intensity between 2 and 5 p.m., which may be 

 ascribed to the maximum of inclination which occurs in those 

 hours ; this was previously recognized in the Milan observa- 

 tions. 



3. In winter the inclination attains its minimum at 6 a.m., 

 and its maximum at 3 p.m. 



Minimum 270'69* 



Maximum 272-02 



Difference 1-33 



In summer the minimum is at 5 a.m., and the maximum 

 at 8 a.m. 



Minimum 289-70 



Maximum 291*23 



Difference 1-53 



The several months show at all seasons a small minimum 

 of the inclination about noon, whence we must conclude that 



* The value of a scale-division = 28-185 seconds of arc. The appa- 

 ratus was set tip in June, 1839, but was not sufficiently steady to give 

 value to the observations with it until August; it continued, however, sub- 

 ject to a tremulous motion occasioned by passing carriages until February, 

 1840, when this disadvantage was remedied. 



