644 
Proceedings of the Royal Irish Academy. 
bodies, viz. the I^'ewtonian law of the inverse square of the distance, 
and product of masses. 
We can at once find the periodic times of the hydrofluoric, hydro- 
chloric, hydrobromic, and hydriodic acid molecules from the fore- 
going :— 
As I have assumed, toi = , equation (4), (conservation of areas) 
Tit 
becomes, by transformation. 
(9) 
^ + 1 m 
From this we find, using the corresponding values of m and p : — 
Angular Velocity and Periodic Times. 
Angular 
Velocity. 
Periodic 
Time. 
+ 1-00000 
1-00000 
HF 
- 1-08482 
0-92181 
HCl 
- 1-04490 
0-95740 
HBr 
- 1-01919 
0-98117 
HI 
- 1-01189 
0-98825 
From all the foregoing I draw the following general conclusions : — 
1. That the hydrogen molecule will combine with the fluorine, 
chlorine, bromine, or iodine molecule only when their rotations have 
opposite directions. 
2. That the rotation of the resultant molecule is opposite to that 
of hydrogen, and in the same direction as that of the second element. 
3. That it is probable that the periodic times of the hydrogen, 
fluorine, chlorine, bromine, and iodine molecules are in the exact 
proportions of 1, 9, 17, 39, and 63. 
