We gave two main reasons in favour of the “weight” definition—(1) it considerably reduces the possibility of confusion over units, (2) it “ legalises “ the almost universal practice of expressing S.I. in seconds. We do not consider that Mr. Greenwood's remarks invalidate our conclusion that the “weight” definition is preferable.

We agree with Mr. Greenwood that provided forces are everywhere measured in earth gravitational units, (S.I.)� is independent of location: this is because the universal use of earth gravitational units is tantamount to using absolute units. But if a true gravitational system of units is employed, (S.I.)m must vary with location