November 16, 1900.] 



SCIENCE. 



745 



criticism of Ostwald (under date Sept. 16, 

 1891): " The electrostatic theory of cohesion 

 is new to me, * * * but for electrolytes there 

 is the question to be answered, why stuffs 

 like alcohol, etc., do not conduct? whilst 

 according to your theory, all elements have 

 electric charges." 



These objections could not be met then, 

 and have not been met up to the present 

 time, in spite of the fact that this new con- 

 cept (of the ionic charge being a funda- 

 mental part of the atom, apart from its 

 chemical functions) has proved a most fer- 

 tile one, and has been considerably devel- 

 oped by the orignator and by later workers, 

 Richartz, Chattock, Lorentz, Larmor and 

 others. N"or will these objections ever be 

 met until we know the nature of metallic 

 conduction. 



This is one of the great outstanding 

 problems. It has long been known that 

 there is a relation between electric and 

 heat conductivity. The writer has shown 

 that there is a connection between the ve- 

 locity of sound (and hence the elasticity 

 and density) and the electric conductivity 

 of wires. J. J. Thomson, as mentioned 

 above, suggested that the current was 

 carried by the electrolysis of molecular 

 groupings, and his later work renders it 

 probable that it is by means of the cor- 

 puscles. It is possible that the atoms of 

 a metal are really dissociated and the 

 negatively charged corpuscles are in a state 

 similar to that of the ions of a solution, i. e. , 

 the metallic atom is not a fixed combination 

 of certain corpuscles, but is constantly 

 changing in composition, the negative cor- 

 puscles being, as it were, in solution in the 

 metal, and changing about freely. 



Such an hj'pothesis would account for the 

 relation between the velocity of sound and 

 the electric conductivity. For the cohesion 

 of the atoms would be due to these nega- 

 tive corpuscles acting, as the mortar be- 

 tween bricks, to bind together the positive 



groupings, and hence the greater the num- 

 ber of free corpuscles the greater the elas- 

 ticity and the greater the conductivity, the 

 conductivity being simply the number of 

 free corpuscles per cubic centimeter. The 

 greater the number of corpuscles in the 

 positive groupings, i. e., the greater the 

 molecular mass, the less the conductivity. 

 In presenting this summary I am aware, 

 of coarse, that much of it is in need of 

 further experimental evidence, and I hope, 

 in time, to supply at least a part of this. It 

 is considered, however, that the scheme 

 here presented has a weight apart from its 

 experimental foundation, in that it is a 

 whole and consistent theory bj- which for 

 the first time all physical phenomena are 

 reduced to the simplest possible elements. 

 Eeginald a. Fessenden. 



ADDRESS OF THE PRESIDENT OF THE SEC- 

 TION OF GEOLOGY OF THE BRITISH 

 AS80CIA TION. 

 I. 

 EVOLUTIONAL GEOLOGY. 



The close of one century, the dawn of 

 another, may naturally suggest some brief 

 retrospective glance over the path along 

 which our science has advanced, and some 

 general survey of its present position from 

 which we may gather hope of its future 

 progress ; but other connection with geol- 

 ogy the beginnings and endings of centuries 

 have none. The great periods of move- 

 ment have hitherto begun, as it were, in 

 the early twilight hours, long before the 

 dawn. Thus the first step forward, since 

 which there has been no retreat, was taken 

 bj' Steno in the year 1669 ; more than a 

 century elapsed before James Hutton 

 (1785) gave fresh energy and better direc- 

 tion to the faltering steps of the young sci- 

 ence ; while it was less than a century later 

 (1863) when Lord Kelvin brought to its 

 aid the powers of the higher mathematics 

 and instructed it in the teachings of mod- 



