The distinction remained confused in many minds, because, for the most part, masses were comparatively estimated by the intermediary of weights.

The estimations of weight made with the balance utilize the action of the weight on the beam, but in such conditions that the influence of the variations of gravity becomes eliminated.

The two weights which are being compared may both of them change if the weighing is effected in different places, but they are attracted in the same proportion.

If once equal, they remain equal even when in reality they may both have varied.
The current law defines the kilogramme as the standard of mass, and the law is certainly in conformity with the rather obscurely expressed intentions of the founders of the metrical system.

Their terminology was vague, but they certainly had in view the supply of a standard for commercial transactions, and it is quite evident that in barter what is important to the buyer as well as to the seller is not the attraction the earth may exercise on the goods, but the quantity that may be supplied for a given price.