

Compound Molecules ivith Theoretical Atoms. 615 



For the study of the compounds of hydrogen and carbon 

 with which we are now concerned three charts are required. 

 A chart showing both the x- and the ^-component forces 

 is required for each of the three combinations, the force of 

 one hydrogen atom upon another, the force of a carbon atom 

 on a hydrogen atom, and the force of a carbon atom upon a 

 carbon atom. Since the axes of all atoms in the molecule 

 are parallel, the components of the force in two directions 

 only are required, the £-axis coinciding in direction with the 

 axis of rotation of every atom, and the .r-axis coinciding in 

 direction with the equatorial planes of the atoms. The 

 making of these charts is a laborious process. It was not 

 known at first to what distances from the atom to extend 

 them. At certain distances they are used much more than 

 at others. In speaking of distances we shall use the small a* 

 unit explained in former papers, which may be converted 

 into centimetres by multiplying by '207 x 10~ 12 . 



PL VIII. fig. 1 shows both the a;- and the --component forces 

 when one hydrogen atom acts upon another. PL IX. fig. 2 

 shows them when a carbon atom acts upon a hydrogen atom, 

 or when a hydrogen atom acts upon a carbon atom. The chart 

 for the case of a carbon atom acting upon a carbon atom is not 

 given, because at the small distances concerned in most of the 

 molecules this force may be found by using the chart for the 

 action of carbon on hydrogen. The field is the same in 

 character, and the force mav be obtained with sufficient 

 accuracy up to distances of 400 or 500 by multiplying the 

 carbon-hydrogen force by the constant 378. This constant 

 is the sum of the squares of the radii of the orbits of the 

 twelve electrons in the carbon atom, as determined in a 

 former paper*. 



In explanation of the charts, one atom is supposed to be 

 located at the origin in the lower left corner with the 

 direction of its axis of rotation along the vertical line, the 

 axis of z, and another atom to be placed anywhere upon 

 the chart having its axis parallel to the first atom. The 

 x-lovce and the c-force between the two atoms in this 

 position may then be read directly by the numbers on the 

 curves passing nearest to it. If it lies between two of the 

 curves the force may be estimated by proportional parts. 

 If the second atom is moved along one of the curves repre- 

 senting the cC-forcethe force is constant along this curve, that 

 is the curves are lines of equal force, the one set for .t* and the 

 other for z. In fig. 1 there are two curves marked zero, the 

 upper curve being that where the £-force is zero, and the lower 



* Phil. Mag., Aug. 1915, equation (12), p. 266. 



