Antoine Furetière

Other (then Mersenne) twofold use of the understanding of the Second : Antoine Furetière (1619-1688):

“La mesure contient ordinairement une seconde d’heure, qui est environ le temps du battement du poux & du choeur: desorte que la systole ou contraction du coeur repond à l’élevation de la main; & sa diastole, ou dilatation, à l’abaissement. Elle dure autant de temps qu’un pendule de deux pieds & demi de long en employe à faire un tour & un retour. ”

So, in bullet points :

1. La mesure = time duration of 1 second (seconde d’heure = 1/3600 of an hour);

2. This is about the time duration of a heart beat;

3. The comparison to the heart beat : the systole is the hand going up, the diastole is the hand going down;

4. This ( la mesure) last the time, a pendulum of 2 1/2 foot needs, to go forth and back (à faire un tour & un retour);

5. The back and forth of a pendulum of 2 1/2 foot = about 1,85 seconds

6. Conclusion : the time duration of the 1 second mesure equals the time of (see point 2) “about” the time duration of 2 seconds (1.85)

7. Is to be understood as : the TIME DURATION of the mesure (1/3600 of an hour) equals the PERIODIC DURATION of (about) 1 ‘periodic’ second.

8. More simplified: the time duration of 1 second equals the perodic time of 1 second, which is in absolute time duration (about) 2 seconds.

9. The confusion becomes clear only when one takes the double understanding of the second (absolute duration / periodic duration) into account.

Closing remark: where Mersenne takes a pure second pendulum, to define the perodic time measurument of the ‘period’ of one second, Furetière speaks about the ‘mesure’ ( mesure ordinaire), for which he apperently takes a kind of avarage of 68/70, the middle of what Mersenne takes for the whole range of mesure ordinaire (60/80).