[November, 
648 Action of Chemical Forces. 
are associated in them. All higher cycles are complex, each 
containing two or more of the primary septenary series, the 
“ oftaves ” of Newlands. The third and fourth cycles have 
each two primary series, with three intermediate elements, 
which latter are the iron group and the first platinoid group 
respectively. The first member of each of these cycles is 
an alkali metal ; the first members of the second septenary 
series in each are metals, copper in the third cycle, silver in 
the fourth, which differ vastly from the alkali metals, but 
which are held to have some analogies with them. These 
analogies are due to atomicity. Copper forms compounds 
in which the metal is a monad, and the only (or almost the 
only) salts of silver are of this class. Silver and copper, 
however, are widely different from alkali metals in most 
other respeCts, notably in being very inactive chemically, 
and in having high densities. Evidently, then, the atoms 
forming the higher cycles have conditions absent from the 
elements of the simple cycles, which impress upon these 
cycles their complex character. In the third cycle elements 
for the first time depart from the primitive order. The first 
element of each primary series is no longer in all cases an 
alkali metal, but may be a metal of a new and distinct type. 
In this new kind of elements the poles are of a second 
order, in which the ratio between chemical attraction proper 
and the attraction of cohesion is changed. Chemical at- 
traction is less and cohesion is greater, — hence the charac- 
teristic inertness of the atom. Chemical activity is a 
function of the two forms of attraction, direCtly of the first, 
inversely of the second. The first proposition needs no 
demonstration, and the second is true because the attradtion 
of cohesion must be overcome before union with unlike 
atoms is possible. 
Atoms are subject to periodic modification as a law of 
their being. There is lithium, and six succeeding elements; 
then again an alkali metal and six succeeding elements, 
repeating the type of the first. The cycle advances by 
transitions, the progression being nowhere broken, but always 
moving regularly from type to type. The third cycle begins 
with an alkali metal, and its second and third elements 
closely resemble their lower atom analogues. Afterwards 
the resemblances are less distinct ; the cycle is in transition 
towards elements of the second order. High atomicity, 
high melting-point, and low atomic volume culminate in the 
iron group ; and the succeeding element, the first member 
of the fourth septenary series, has poles of the second order. 
Chemical activity is least at this point, and density, melting- 
