Alfred Marie Cornu. 187 



due the elegant geometrical construction in which spirals are applied 

 to express graphically the relative intensities of the light in diffraction 

 images. His preference for geometrical demonstrations of theorems, 

 which might otherwise be hidden under a burden of analytical 

 symbols, was well known. He worked acoustics in conjunction with 

 M. Mercadier, and investigated the values of musical intervals in the 

 case of melody and in the case of harmony, which it is known are not 

 necessarily coincident. He examined experimentally the torsional 

 vibrations which accompany the transverse vibrations of violin strings, 

 In conjunction with M. Bailie, he redetermined the constant of gravi- 

 tation. He was occupied, too, with the problems of synchronisation 

 of two resonant systems capable of vibration under elastic forces, 

 these memoirs being publishecl in 1888 and 1889, the second of them 

 including the application of his ideas to the synchronisation of clocks 

 for the distribution of time. His plan was closely akin to that of 

 Wheatstone, depending on the sending, at every second, of feeble 

 induction currents generated by the movement of a magnet attached 

 to the 'pendulum of a master clock. In 1884 he reported on the 

 electric transmission of power by M. Marcel Deprez on the Chemin de 

 Fer du Nord. He took part in the first electrical congress at Paris in 

 1881. In 1886 he became a member of the Bureau des Longitudes, 

 and of the International Bureau of Weights and Measures. For the 

 former body, in which he took great interest, he did much to perfect 

 the " Annuaire," to which he contributed some exceedingly valuable 

 and authoritative essays on electric phenomena from the modern 

 standpoint, on star spectra, on electric generators, and on polyphase 

 currents. On the International Bureau of AVeights and Measures he 

 worked at the construction of the new standards, insisting, against 

 considerable opposition at first, on the advantage of adopting a highly 

 polished surface upon which to engrave the fiducial marks in the new 

 metre standards. To his pen as reporter, after the death of M. Tresca, 

 is due the report of the International Bureau, recording the transition 

 from the old " metre des archives" to the ''prototype provisoire," 

 which in turn led to the " metre prototype international." 



Cornu was twice President of the Societe de Physique, of which, 

 indeed, he was one of the foundation members. He took an active 

 interest in its meetings, and contributed much to its success. He was 

 also President of the Academic des Sciences ; and by general consent 

 was elected to preside over the International Congress of Physics in 

 1900. He was elected a Foreign Member of the Eoyal Society in 

 1884, and had previously, in 1878, received the Rumford Medal for 

 his work on the velocity of light. He was also an Honorary Member 

 of the Physical Society of London. At least twice he gave Friday 

 evening discourses at the Royal Institution ; the last of these, in 1895, 



