164 TRANSACTIONS OF SECTION B. 



In the following year, at Birmingham, Sir W. Crookes devoted his address 

 to this Section to an exposition of his ideas of the ' Genesis of the Elements,' 

 a subject to which he on many subsequent occasions returned, and amplified in 

 the light of recent discovery. The process of evolution of the elements from a 

 primal ' protyle ' is depicted as taking place in cycle after cycle, in each cycle 

 the ' unknown formative cause' scattering along its journey clusters of particles 

 corresponding to the atoms of the ' elements,' forming in this way a series such 

 as that beginning with hydrogen and ending with chlorine ; a repetition of the 

 movement under somewhat altered conditions giving rise to a series of similarly 

 related elements, and thus homology, which is shown by the members of the 

 natural families, is provided for. 



The investigations of Sir J. J. Thomson on the discharge of electricity 

 through gases have established the divisibility of the atoms, and in his ' Cor- 

 puscular Theory of Matter ' he has given us conceptions of how atoms may he 

 constituted to provide a series so related that they reflect, if not reproduce, 

 many of the chemical characters of the elements and their periodic relation to 

 atomic weights. 



With the discovery of radium and its remarkable properties we have been 

 brought in contact with an element undreamt of in our philosophy. The inter- 

 pretation of the results of the investigation of this element has called for 

 drastic changes in our conception of an element. The pursuit of the researches 

 of the radio-active elements, guided by the theory of the spontaneously disin- 

 tegrating atom propounded by Rutherford and Soddy, has served to reveal facts 

 which lend a special emphasis to many passages in the address of Sir W. Crookes 

 to which I have already referred. 



For instance, the passage in which he said : ' Should it not sometimes strike 

 us, chemists of the present day, that after all we are in a position unpleasantly 

 akin to that of our forerunners, the alchemists of the Middle Ages ? The necro- 

 mancers of a tune long past did not, indeed, draw so sharp a line as do we 

 between bodies simple and compound; yet their life-task was devoted to the 

 formation of new combinations, and to the attempt to transmute bodies which 

 we commonly consider as simple and ultimate — ^that is, the metals. In the 

 department of synthesis they achieved very considerable successes ; in the trans- 

 mutation of metals their failure is a matter of history.' 



Or again, when he propounded the question, ' Is there, then, in the first 

 place, any direct evidence of the transmutation of any supposed " element" of 

 our existing list into another, or of its resolution into anything simpler ? '—a 

 question to which he, Sir William Crookes, was at that time forced to reply in 

 the negative, whereas to-day many instances might be cited in support of an 

 affirmative answer to this question. Radio-activity has supplied a method of 

 analysis— radio-active analysis— surpassing in delicacy any of the previously 

 known methods for the examination of material substance; the application of 

 these methods has not only added to the list of elements but also new classes of 

 elements. First, elements indistinguishable and inseparable by chemical means, 

 yet differing slightly but definitely in their atomic weights. The existence of 

 these ' isotopes,' as Soddy styles them (a name giving prominence to the fact 

 that such elements occupy the same place in the table of the elements), demon- 

 etrates that absolute uniformity in the mass of every ultimate atom of the 

 same chemical element is not an essential, but that ' our atomic weights merely 

 represent a mean value around which the actual atomic weights of the atoms 

 vary within certain narrow limits.' - 



Whether the possibility of separating isotopes, recently suggested by Dr. 

 Lindemann and Dr. Chapman, will be found capable of experimental realisa- 

 tion, must be left to the future to decide; in fact, in this matter we must 

 adopt the attitude, prevalent in other than scientific circles, of 'wait and 

 see.' 



The investigations in the field of radio-activity have further brought to light 

 that identity in atomic weight may be associated with difference in chemical 

 properties, revealing the existence of a further class of elements for which 

 Dr. Stewart suggests the name ' isobares.' Further, Dr. Stewart considers that 



" Crookes. Address to Section B. 1886. 



