334 



Lord Kelvin on the 



attractions between the positive atoms and the negative atoms 

 of neighbouring molecules to keep them in lines through the 



Fig. 1. 



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centres of the molecules, as fig. 1 shows for the undisturbed 

 condition of the system, and fig. 2 for the system subjected to 

 the supposed elongation. Hence two of the three diameters 

 through atoms of each crystalline molecule are altered in 

 direction, by the elongation, while the diameter through the 

 third pair of atoms remains unchanged, as is clearly shown in 

 fig. 2 compared with fig. 1. 



§ 6. Remark, first, tha$ the rows of atoms, in lines through 

 the centres of the crystalline molecules, perpendicular to the 



