By this last operation our equation has now achieved a form which requires only one more transformation to bring it into line with Newton’s formula. Instead of writing:
r³ / t² = c
we write:
r / t² = c (1 / r²)
All that now remains to be done amounts to an amplification of this equation by the factor 4ϲm, and a gathering of the constant product 4ϲc under a new symbol, for which we choose the letter f. In this way we arrive at:
4ϲmr / t² = 4ϲcm / r²
and finally:
P = … = fm / r²
which is the expression of the gravitational pull believed to be exerted by the sun on the various planetary bodies. Nothing can be said against this procedure from the point of view