application of such a force longitudinally. It comes out at 320 miles in diameter. Having thus found the force, we can now determine the numerical value of the ethereal coefficient of mass attraction for the particular units chosen, namely, the metre as the unit of length, the kilogram as the unit of force, and a mass of 9.81 kilogram weight as the unit of mass. The result of this calculation is
The symbol means that 10 is to be multiplied 10 times with itself. The numerical expression for may also be written in the form
where the minus sign of the exponent signifies that 6.47 is not to be multiplied, but divided by .
In the above example showing how the ethereal coefficient may be determined for any arbitrary system of units, I have taken as the unit of mass the mass of 9.81 kg.; this was merely done as a matter of convenience, so as to be able to regard the kg. as the unit of force, as is customary in engineering. It is, however, more in consonance with first scientific principles not to fix arbitrarily a
