320 MM. Struve and Dollen on the Correction 



can it be doubted that, through the employment of the cor- 

 rection thus obtained, the directly observed latitude will he 

 brought nearer to the mean latitude, and will become thereby 

 more fitted for the determination of the mean figure of the 

 earth ? That the disturbing influence brought into the calcu- 

 lation in this manner is only a portion of the whole existing 

 disturbance — and this for two reasons : first, because only the 

 recognizable inequalities in the distribution of mass upon the 

 surface of the earth, not the equally probable ones beneath it, 

 can be taken into account; and secondly, because of these only 

 such portion can be considered, as the actual extension of the 

 levelling may have supplied data for — this is indeed to be 

 regretted, but can be no reason for refusing to take account 

 of it, even if it should perhaps prove probable or even certain 

 that only a relatively small portion of the disturbance would 

 thus ever be brought to our knowledge. The matter becomes 

 plainer to the mind by an instance : suppose an astronomical 

 station situated at the foot of the great pyramid of Cheops; let us 

 say, in the middle of the southern side. We have not ourselves 

 selected this station; we find it among the materials at our dis- 

 posal, which we have to use to the best of our ability, for the 

 determination of the figure of the earth. Can there be a doubt 

 as to whether or not the correction of //# 7 to the observed lati- 

 tude at this station, which Peters has calculated for such a 

 case, should be accepted, or whether a computer would be 

 right who from prudence should entirely exclude this latitude ? 

 And if the correction is here obviously necessary, is the matter 

 different if, instead of the pyramid, we think of Schehallien ? 

 or even, instead of this isolated mountain mass, of some more 

 extensive inequality of the earth's surface, equally and, as 

 regards its mass, as correctly known ? In such a case we cer- 

 tainly cannot tell quite as well as in the case of an isolated 

 mountain how far we should extend the calculation ; this, 

 however, makes no important difference. The answer to the 

 question "how far?" is a decided one : — in every case, as far 

 as possible; ten miles' distance is better than five; five is better 

 than one ; one better than none at all. 



" In the foregoing remarks we have endeavoured to the best 

 of our knowledge to bring forward and to place in the clearest 

 light every thing that we can say in favour of the views which 

 General Schubert maintains so warmly; and we acknowledge 

 readily that a certain force in these arguments is not to be 

 denied. If nevertheless, after mature deliberation, we must 

 needs express ourselves as quite opposed to this opinion ; in that 

 we, in the present state of things, are not only far from con- 

 sidering as necessary the levellings recommended, but rather, 



