CONDITIONS OF CONTINENTAL ICE. 235 



pressure of the particle a that moves the particle b in 

 front of it, and the pressure of the particle b that moves 

 the particle c, and so on, but that each particle moves 

 by its own weight, we are nevertheless led to the same 

 conclusion. The weight of the particle (the force of 

 gravity) will not move the particle unless the particle 

 is allowed to descend. If a particle moves by its own 

 weight from the centre of the sheet to the circumfer- 

 ence, it must descend: it must pass from a higher to a 

 lower level. It must move down an inclined plane 

 from the centre to the circumference, but to allow it to 

 do so the sheet must be thickest at the centre."" 



If, on the other hand, we adopt the "Molecular" 

 theory, or the "Dilatation" theory of the motion of the 

 ice, or any other theory whatever which attributes the 

 motion of the ice not to gravity, but to some expansive 

 force acting in the interior of the mass, we are equally 

 led to the same conclusion as to the greater thickness 

 of the sheet at the centre. Although such a force will, 

 of course, tend to push the ice as powerfully inwards 

 in the direction of the Pole, or centre, as outwards in 

 the direction of the circumference, yet the motion of 

 the ice will always take place in the latter direction, 

 and never in the former, for the latter will always be 

 the direction of least resistance. The tendency of such 

 a force is to produce an outward motion of the ice on 



* That the entire mass of the Antarctic ice down to the bottom is 

 in a state of motion, and not simply the upper layers, as some 

 suppose, is demonstrable from the fact that icebergs are stratified 

 down to their base. The iceberg is simply a piece broken oil the 

 edge of the sheet, and the stratified face of the berg is the counter- 

 part of the edge from which it broke off; and as the icebergs are 

 known to be stratified to their base, it proves that the sheet from 

 which they were derived is likewise stratified to the bottom. The 

 fact, therefore, that stratified icebergs are continually breaking oil' 

 the Antarctic sheet, and have been for ages, proves that the sheet 

 down to its bottom must have been in a state of outward motion. 



