B. TEKRESTRIAL PHYSICS AND METEOROLOGY. 91 



path. Thus has it frequently happened that a very inflam- 

 mable roof has been protected by an iron knob, when, as is 

 frequently the case, this, the highest portion of the buildings 

 is first struck. Verein sacks Ingen.^ 1872, 8. 



BAEOMETRIC DETERMINATIOX OF ALTITUDES. 



Monsieur Montigny has laid before the Academy of Sciences 

 of Belgium the results of a series of experiments made on the 

 sj^ire of Antwerp Cathedral, in w^iich he determined baro- 

 metrically the heights at several points in Avinds of different 

 directions and velocities. His tables show a difference be- 

 - tween the calculated height and the real height, the latter 

 beino- o-reater for winds in the eastern semicircle, while the 

 former is greater for Avesterly winds. In north and south 

 Avinds, and those closely neighboring, the heights measured 

 both ways closely agreed. The differences between true and 

 barometric altitude increase regularly, according as the ob- 

 server stands on the east and west or north and south sides 

 of the spire. The height, as measured by the barometer, in- 

 creases as a rule with the velocity of the wind. No connec- 

 tion was found between barometric height and the inclina- 

 tion of the wind. Observations at Namur and Brussels, 

 compared with those at Antwerp, show a systematic varia- 

 tion like that just described. 12 B, 1873, 375. 



THE LOCAL DEVIATION OF THE PLUMB-LINE. 



Baeyer communicates to the Royal Prussian Academy of 

 Sciences a note with resjard to the local deviation of the 

 plumb-line, and its influence upon accurate levelings. ' Upon 

 the Brocken, the absolute latitude is 10" greater than that 

 which is computed for the same spot by triangulation, con- 

 nectincj it with the Seeberoje. Three miles north of the 

 Brocken, at Hornberg, the observed latitude is 4" greater 

 than the computed. If, now, we assume that at a greater 

 distance, as, for instance, at Wolfenbuttel, these discrepancies 

 diminish, so that observation and computation agree, then it 

 must follow that between Seeberge and Wolfenbuttel there 

 exists a northerly deviation of the plumb-line; that is to say, 

 a deviation such that the zenith of the plumb-line is north 

 of the normal zenith, and that the northerly deviation greatly 

 increases from the vSeeberge to the Brocken, where it reaches 



