Mass

In a word, the masses of bodies are conventional data defined by the fact that they are proportional to the accelerations caused by one and the same force.

To put it differently, the mass of a body is the quotient of the force which acts upon it by the acceleration given to it.

Poincaré used to say picturesquely, quote, Masses are coefficients which it is convenient to use in calculations, unquote.

If there is one property of bodies which comes within the range of our senses, a property of which every man has some sort of instinct or intuition, it is mass.

Yet careful analysis shows us that we are unable to define it otherwise than by disguised conventions.

Poincaré's definition seems paradoxical in its admission of powerlessness, but it is correct.

Mass is only a coefficient, a conventional outcome of our weakness.

Nevertheless, something remained upon which we thought we could base, if not our craving for certainty, genuine men of science gave up the idea of certainty long ago, at least our desire for accuracy of deduction in our classification of phenomena.

From that moment he went back to all his old habits of piety and never again gave them up.

Every morning he might be seen early at St. Sulpice, where he heard Mass before he began his work.

Every evening he said a decade of the Rosary, a practice which his pious mother had instilled into all her children.

On Sundays the parishioners of St. Sulpice often admired this illustrious stranger, with his noble and serious bearing, and a look of profound recollection, kneeling devoutly before the altar.

He treated his body as a slave, or rather as a beast of burden, whose function was simply to execute the orders of his soul.

His whole life was one of regular and uniform labor.

Up at five o'clock every morning, he was always at church by six o'clock, when he heard Mass and made his meditation.

At seven o'clock he would go and see the sick in the hospital, and then shut himself up in his room to work hard until ten o'clock.