de toute nécessité, absoîutely necessary

6. Wollaston (1766-1828), noted English physicist and chemist; has been called the founder of modem British chemistry.

7. M. Becquerel (1 788-1878), French physicist of distinction.

Page 170. — i. remarquable au même titre que, equally remarkable witk.

2. M. de la Rive (Auguste, 1801-1873), Swiss natural philosopher, who devoted much time to investigations in electricity.

Page 171. — 1. au fur . . . formation; cf. page 21, note 5.