156 



B. V. KOTLIAREVSKII 



£"„, = 10% and the second for E^ = 15%. To compare these nomograms 

 in formula (30), a should be replaced by its value from formula (29). 



All the nomograms are drawn for the case — < 1, i.e. supposing that 

 within the limits of one extreme point of gravity there are not less than 



two points of observation. It was also supposed that — - >2; observations 



P 

 of this inequality require that each extreme point is mapped by not less 

 than two isoanomalies. 



10 



5 -JT 



0-2 



0-4 



0-5 



«-0 



Fig. 12. 



It is difficult to find from the nomogram (Fig. 11), for a given E^, values 

 of for large values of -— or small values of — for any values of 



go 



8q 



It IS also difficult to find from given values of D^ and — a value of — from 



o / 



r ''0 



the nomograms (Fig. 12) for — > 0.4 and from the nomogram (Fig. 13) 



for — > 0.5. 



The reason lies not in any defects of the nomogram or formulae, from 

 wliich they were calculated, but in the very nature of the formation of total 

 errors of the field and errors of the increment of gravity between two isoano- 

 malies. Since the errors E^ and D^^ are made vip of errors in the observations 

 and interpolations for certain relationships between the elements of the 

 field and the parameters of the surveys, the values of the separate parameters 



