PRESIDENT’S ADDRESS—SECTION B. 63 
that his paper is a very valuable contribution to the study of the 
causes underlying the periodic law. 
By the adoption of a form of zigzag curve Emerson Reynolds 
succeeded in indicating much more clearly than by the ordinary 
tabular system, the relations and contrasts between the various 
members of the different periods, bringing into prominence 
especially the following noteworthy points :—(1) The possibility 
that hydrogen is not the 77st member of Mendeléett’s first period, 
but the Zas/—in other words, that there is still room for elements 
of lighter atomic weight than hydrogen. (2) The possible non- 
existence of Mendeléeff’s ninth period, which includes at present 
only the metal Zrdium ; and (3) the interperiodic character of the 
triplet groups Fe. Ni. Co., Rh. Ru. Pd., and Ir. Os. Pt. 
Crookes, in his lecture on the ‘Genesis of the Elements,” 
adopted a slightly modified form of the curve proposed by 
Reynolds, and of it he says, ‘“‘The more I ponder over the 
arrangement of this zigzag curve the more I become convinced 
that he who fully grasps its meaning holds the key to unlock 
some of the deepest mysteries of creation.” Using it as an illus- 
tration, he sketches out a possible evolution of the substances known 
to us as elements from an original or primordial matter, which he 
calls protyle, and in this sketch he explains the possible formation 
of such groups as the three triplets already referred to, and that 
of the Cerium metals, the characteristics of which he has done so 
much to elucidate. While on this subject of the graphic repre- 
sentation of the periodic law, attention should be drawn to a 
curious paper by the Rev. Dr. Haughton, read before the Royal 
Irish Academy in 1888, in which, by a geometrical representation 
of the law, he brings out some interesting and hitherto unnoticed 
points, and indicates in a very graphic manner the isolation of 
hydrogen and the points at which, in his opinion, there are still 
to be found missing elements. 
The other line of investigation, which has led to serious doubt 
as to the accuracy of the hitherto generally accepted notions of 
the nature of the so-called elements, is the purely experimental, 
as developed by Crookes and others in researches on the rare- 
earth metals. By long and tedious experiments Crookes has 
succeeded in splitting up y¢trviuzm, for example, into several sub- 
stances, which are, at any rate, spectroscopically distinct, but 
which are so closely related chemically that they are indistinguish- 
able by ordinary methods. He believes it will be possible to 
obtain similar results with other substances, if only the right 
methods can be found ; in fact, he has actually found indications 
of the commencement of a like separation in other cases than that 
of yttrium. Reasoning on these facts he has modified his views 
as to the character of the elements, and is now inclined to regard 
them, not as made up of a number of atoms of rigorously the same 
weight, but as consisting of groups of atoms of which the mean 
