French Brumaire-class submarines fitted out with liquid cooled piston caps according to the Dutch magazine Marineblad dated 1913-1914 no. 6

An item reported that the diesel engines placed in the French Brumaire-class were to be fitted out with oil- or water cooled piston caps. For the time being possessed the boats over just 60% of their horsepower causing a limited speed of 10 instead of 10 knots.(1)

Note
1. Preceded by the Pluviôse-class and succeeded by the Archimède numbered the Brumaire-class submarines of the Laubeuf-type 16 boats built between 1911-1913.