translate English to French: Generally speaking, one may say that a simple mechanical watch (hours, minutes and seconds hands) should include at least fifteen jewels located in the places most subject to wear due to friction.
De manière générale, on peut dire qu'une montre mécanique simple (heures, minutes, secondes) devrait en principe contenir au minimum quinze rubis placés aux endroits exposés à l'usure due au frottement.