24 



OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



Referring back to Fig. 1 the attraction of a mass, centred at 

 C, is exerted at the station 8 in the direction C S. We have 

 already considered the variation in the horizontal component, and 

 in Table I the proportionate variation in this, with a varying 

 distance of the station, is given ; it is obvious that these same factors 

 apply equally to the vertical component of the force, if the angle 

 is measured from the vertical, instead of the horizontal, plane. 

 The effect of any small mass, situated on the vertical drawn through 

 C, will reach a maximum value when the angle joining it to the 

 station S makes an angle of about 54° 45' with the vertical, and 

 at any greater or less depth the effect will diminish in the propor- 

 tions given in Table 1. 



So far we have only considered the case of a single small mass 

 represented by C, but it is obvious that every other similar mass 

 situated at the same depth and distance from S will have the same 

 effect; and if, instead of the line C S, we consider, as is shown in 

 fig. 2, the space included between the surfaces of two cones and 



/ 



.* 



o 



-C- 







— - — - - « . 



Fig. 2 



two vertical radial plane surfaces, both diverging from each other 

 at a very small angle, and instead of the horizontal line C V 

 we take a very thin layer included between two horizontal planes 



[ 172 ] 



