1 835 . ] Improvements in Science . 1 03 



The westerly deviation is therefore greater than the 

 easterly. 



In the following table the time is exhibited during which 

 the needle remains to the west and east of the magnetic 

 meridian : — 



WESTERLY. EASTERLY. 



March . . 10 h 20' - 13 h 40' 



May ... 10 — - 14 — 



June ... 10 — - 14 — » 



August . . 8 — - 16 — 



September . 8 20 - 15 40 



November . 8 — - 16 — 



December .13 — - 11 — 



The inclination of the needle near Freiberg is stated by 

 Humboldt to be at 250 metres (273*41 yds.) under the 

 surface, 67° 35'*5, and on the surface, 67° 32'*99. 



Reich (Pogg. xxxi.) gives the result of three years, not 

 the mean however, of the monthly summary, but of the 

 whole year : — 

 1831. 67°24'-80. | 1832. 67° 22'-65. | 1833. 67° 20'- 15. 



Lohrmann ascertained the inclination for Dresden to be 

 67° 26'*34. The observations in these instances were made 

 with Gambey's modification of the magnet for measuring 

 the inclination. 



The declination of the needle at Sitka, on the NW coast 

 of America, according to Erman, is 28° 19' E, the inclina- 

 tion 75° 43'. 



IV. PNEUMATICS. 



Mean Height of the Barometer at the Sea. — This is a sub- 

 ject which has latterly attracted much attention. Professor 

 Schouw of Copenhagen, more especially (Poggendorff's 

 Ann.) has collected numerous good observations, and has 

 drawn some remarkable inferences, which are strikingly 

 corroborated by the following tables, extracted from my 

 own observations with an excellent instrument made by 

 Cary. They illustrate an interesting law by which the 

 barometer is depressed as we approach the equator. 



The numbers are corrected for temperature by the 

 attached thermometer. The observations were made at 

 10. a. m. 



