28 MAGNITUDE, FIGURE, AND 



Mathieu made similar determinations on the parallel of 

 Bourdeaux, Figeac, and Padua, to Fiume.( 19 ) These pen- 

 dulum results, taken together with those of Sabine, give for 

 the whole northern quadrant the ellipticity of -g-^-g- ; but if 

 divided into two parts, the results are far less accordant, ( 20 ) 

 *. e. from the equator to lat. 45 -g-fg-, and from lat. 45 to 

 the pole -s-i-B- The influence of the presence of the denser 

 kinds of rock, such as basalt, greenstone, diorite, and mela- 

 phyre, as compared with the specifically lighter sedimen- 

 tary and tertiary formations, as well as the effect of volcanic 

 islands, ( 21 ) in increasing the intensity of gravity, has been 

 recognised in most cases in both hemispheres ; but there 

 still remain anomalies which are not wliolly explained by 

 the geological character of the rocks accessible to our 

 observation. 



For the southern hemisphere we possess a small series of 

 excellent observations, thinly scattered, however, over a wide 

 extent, by Freycinet, Duperrey, Fallows, Liitke, Brisbane 

 and Eumker, [and Foster] . They confirm what had already 

 appeared so strikingly from the observations in the northern 

 hemisphere, that the intensity of gravitation is not the 

 same at all places having the same latitude ; so much so, 

 that the increase of gravity from the equator to the poles 

 would appear to be subjected to unequal laws under dif- 

 ferent meridians. Lacaille's pendulum experiments at the 

 Cape of Good Hope, and those made in the Spanish voyage 

 of circumnavigation of Malaspina, might have caused it to 

 be believed that the southern hemisphere was in general 

 considerably more flattened than the northern one; but, as 

 I have already stated, ( 22 ) more exact results at the Falkland 



