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to test the methods of reductions by this theory, the stations were 

 arranged in five groups according to the topography. The anom- 

 alies with and without regard to sign for the several classes of topog- 

 raphy and for the two methods of reduction — one taking into 

 account the topography and compensation, and the other only 

 the topography — -are given in Table I. To make it easier to refer 

 to these methods the first will be called the Hayford method and 

 the other the Bouguer method. 



TABLE I 



Mean Anomalies 



This table shows that the Hayford reduction gives about the 

 same values without regard to sign for each class of topography 

 while the mean anomalies with regard to sign have a very small 

 range if we do not consider the 27 stations at the coasts. It is prob- 

 able that the coast stations are affected by the presence of Cenozoic 

 formation, the material of which is lighter than normal. This will 

 be referred to later. We may conclude, I think, that there is prac- 

 tically no relation between the sign and the size of the Hayford 

 anomalies and the character of the topography on which the stations 

 are located. 



We find entirely different conditions in regard to the Bouguer 

 anomalies. The size of the anomaly without regard to sign at 



