of Latitudes for Local Attraction, 323 



to those which correspond with the mean figure of the earth, 

 and are therefore also better fitted for the determination of this 

 mean figure. It will be seen at once without special reminder 

 that this is exactly the case of Schehallien ; and it will be ob- 

 vious that our willingness to allow the said correction to hold 

 good in this case is in no way founded on any confidence in 

 the assertions and deductions furnished by geology, but on 

 the latitude on the other side of the mountain, and on the fact 

 that, as the outcome of the whole investigation, a correct value 

 has been found for the mean density of the earth; this is pre- 

 cisely what was demanded by the condition stated above, only 

 in reverse order. Two further remarks, however, present 

 themselves here to our mind, which seem to us sufficiently 

 worthy of notice to permit a short interruption of the strict 

 course of our argument. In speaking of the correct value of 

 the density of the earth, we regard it as if it were known from 

 other sources, whereas we are perfectly aware, not only that 

 the determination of the same was the especial object of these 

 very observations, but also that it was precisely these observa- 

 tions on Schehallien that gave the first conception of the 

 earth's density. The fact is, however, that it is only the con- 

 firmation which this determination of the density of the earth 

 has since received, by means of the decisive experiments with 

 the torsion-balance, that enables us to acknowledge the force 

 of any such proof — as will be seen when similar efforts made 

 upon Chimborazo and Mimet are remembered. For it is clear 

 that this method of determining the density of the earth lies 

 open to the same objection which Ave make to the justification 

 of correction of latitudes. Indeed, on closer examination we 

 find that in this case the objection has even greater force; for 

 as regards latitudes, something would at least be gained if 

 only in general, that is, on an average of many cases, an im- 

 provement were effected by this procedure ; whereas here, on 

 the contrary, a determination of the density of the earth is 

 supposed to be obtained in each case. But in fact nothing has 

 been attained but some information as to whether or not the 

 unknown disturbances of the direction of gravity affect the 

 two points of observation differently; and it is clearly unrea- 

 sonable to consider a widely aberrant result being due to such 

 disturbances, and, on the other hand, to allow a closely ac- 

 cordant result to count as a true determination of the earth's 

 density. Consequently, in one case as in the other, at Chim- 

 borazo as at Schehallien, these researches, for all that we can say 

 at present, possess an exclusively geological interest ; and to 

 this we must add that even if a great number of sack determi- 

 nations were to hand, the whole of them could tell us nothing 



