25+ Lieut. Zahrtmann on the Mathematical 



M. Janvier is another who is possessed of considerable know- 

 ledge in clock-making, but has not yet applied it to the manu- 

 facture of chronometers. 



M. Fortin is 72 years old ; he is a provincial by birth, and 

 came when quite young to Paris, where he commenced busi- 

 ness in some of the most humble workshops. He has al- 

 ways worked very assiduously, but has beeu unable to raise 

 a fortune by his labours. M. Fortin first attracted notice 

 by the perfection with which he executed balances and pneu- 

 matic machines : he still works, and with much accuracy, 

 notwithstanding his advanced age ; and in the construction 

 of measures, barometers, and pneumatic machines, he has 

 scarcely ever been surpassed. The most remarkable instru- 

 ment which has left his workshop is the great meridian cir- 

 cle erected at the observatory, to which it was presented by 

 the Duke d'Angouleme. This instrument is in imitation of 

 the Greenwich circle, but the divisions are executed in a dif- 

 ferent manner, peculiar to M. Fortin ; the fastening of the radii 

 at the centre is more firm in his instrument, and the divided 

 limb is formed of an alloy of gold and palladium, a sixth part 

 of which consists of the latter metal ; this combination, without 

 becoming oxidated like silver, and without being too hard for 

 the dividing point, as platinum is, produces a metal upon 

 which the divisions are very easily discerned. M. Fortin 

 possesses a dividing instrument which he has been for 40 years 

 endeavouring to perfect, and of which he makes a profound 

 secret; but notwithstanding all his care, his repeating circles 

 are far from being correct with regard to division. He is a 

 member of the Legion of Honour, and received a gold medal 

 at the exhibition of 1819. — M. Fortin has no son, but will be 

 succeeded by M. Herman, a man of 37 years of age, and a 

 native of Dresden, who has married his youngest daughter. 

 M. Herman has resided 16 years in Paris, where he has been 

 under several masters ; and he worked for a considerable time, 

 under M. Fortin's direction, upon the meridian circle. M. 

 Fortin lives at No. 14, Rue des Amandiers, near St. Gene- 

 vieve. 



M. Gambey is a native of Champagne, and is 26 years 

 old ; he began his career at Paris as a clock-maker, but has 

 since devoted his time to the construction of instruments : he 

 is a man of great merit, and who does not confine himself to 

 imitation ; he has made for the observatory a great equatorial, 

 to be moved by a pendulum : the circle is three feet in diame- 

 ter, and is divided upon its edge in equal divisions of 5' ; the 

 reading is effected by two microscopes furnished with micro- 

 meters, and placed upon projecting arms from the centre 



of 



