47 8 Intelligence and Mtscellaneoiis Articles. 



which a portion was reduced to powder and acted upon by hydro- 

 chloric acid, whicli soon brought it into a gelatinous state. The re- 

 sult of this analysis was 



" Silica 37-84 



Alumina 17-99 



Lime 35"18 



Protoxide of iron 6-45 



Masmesia 2-81 



100-27 

 The mean specific gravity from four weighings of the crystallized 

 idocrase was 3-346, that of the fused, agreeing with Magnus, was 

 2929 — 2-94]. — Poggendorff's Annalen der Physik nnd Chimie, No. 

 10, 1838. 



TERRESTRIAL MAGNETISM. 



In a memoir presented by M. Quetelet to the Royal Academy of 

 Brussels, in which he examines the results of the observations which 

 he has made during twelve years upon the state of terrestrial magne- 

 tism at Brussels, the result of the whole of these observations is 

 stated to be, that the magnetic needle has been constantly approach- 

 ing the meridian line, that is to say, that the declination and the dip 

 have diminished from year to year, contrary to what had been ob- 

 served before, at least as to magnetic declination. The results ob- 

 served were as follows : 



This year's observations for the declination were made on the 29th 

 of March. The value indicated is the mean of two series of obser- 

 vations, which gave successively 21o53',l and 21"54',2. Similar ob- 

 servations had been made the evening before, in less favourable cir- 

 cumstance.=;, on account of the agitation of the air. The latter had 

 given for the declination 21''51',3 and 21°51',1 : it was thought that 

 preference should be given to the former. In these different series 

 of observations the meridian was determined by placing the mag- 

 netic apparatus previously in such a manner that the telescope might 

 be directed at pleasure on the middle wire of the transit of the ob- 

 ser\'atory. 



