22 Messrs. A. C. and A. E. Jessup on the 
us iron, carbon, calcium, silicon, and magnesium, whose 
presence is first evidenced by their enhanced lines, as shown 
by Sir Norman Lockyer. The enhanced lines of the elements 
are known to be due to the elements being submitted to very 
high temperatures or very great electric stresses. Inasmuch 
as we are justified in assuming the existence of stresses in the 
stellar systems, it is justifiable to assume the existence of 
enhanced lines as first evidences of evolution. Moreover, it 
may be pointed out that the appearance of new lines in the 
nebula? is generally accompanied by a faint continuous 
spectrum, usually in the green. Hence, in the heavens, it 
would seem that we have distinct evidence of evolution. 
Now Mendeleeff has arranged the elements in order of 
atomic weight, and in such a way that they fall into groups, 
and we may regard the evolution as taking place in one of 
two ways. Firstly, that the elements evolve in order of 
atomic weight, that is along horizontal lines of MendeleefFs 
table ; secondly, that they evolve in groups, that is, down its 
vertical columns. We have strong reasons for believing that 
the second method has most evidence in its favour. 
In the first place, the elements which appear after hydrogen 
and helium are carbon, silicon, magnesium, calcium, and iron, 
but these are in no way in order of their atomic weights, and 
moreover sodium, although much smaller quantities of it can 
be detected, and with a much lower atomic weight than 
calcium or iron, does not appear until long after these 
elements. The first positive evidence of sodium is in the 
case of the stars of group 7. 
Secondly, the whole of the nitrogen group is missing in 
the sun. On the supposition that the elements grow in 
groups, the fact that nitrogen did not form in the sun would 
account for the absence of the other members of its family. 
The other method of growth would imply, that each of the 
five elements belonging to the group was missed out in the 
ordinary process. 
Our view of evolution will at once explain two great 
difficulties connected with the Periodic Table, namely, the 
cases of tellurium and argon, with atomic weights greater 
than those of iodine and potassium. It is natural to assume, that 
if an element A has a greater atomic weight than an element B, 
the element formed from A will also have a greater atomic 
weight than that formed from B ; but this is not necessary, 
and the two cases cited above are examples of this fact. 
Sodium, with a greater atomic weight than neon, forms 
potassium, which has a less atomic weight than argon. 
However, to return to the first stage of evolution. The 
