Editorial Comment. 3 ^ ^ 
The same difficulty is met if we approach the subject from 
another point. A cooHng globe must pass through a con- 
dition in which the surface is cold and the interior still hot. 
Consequently, as has been pointed out by other physicists, 
there must arrive a time when the inner portion, continuing to 
contract, will be in a state of tension — lateral tension — being 
strained over an internal sphere that retains to a much greater 
degree its primaeval heat, and consequently its primaeval size. 
Outside of this the cold superficial layer being compelled to 
sink and unable to contract, must suffer compression later- 
ally. There must, therefore, exist between these two por- 
tions a neutral shell, or layer of no strain, as it has been well 
named, where neither compression nor tension can act. Now, 
the mathematical physicists have told us that in any admis- 
sible time since incrustation took place this layer of no strain 
cannot be deeper than seven or eight miles. But the geol- 
ogist demurs and says that he finds places, as in Pennsylva- 
nia and in the Alps, where palaeozoic strata have been folded 
and exposed by erosion revealing a depth greater than this 
•figure and showing, consequently, that the layer of no strain 
is much deeper than the mathematical conclusion allows. 
Prof. Geikie then argues thus: "If a white hot lava ocean 
enveloped the globe 20 or 25 millions of years ago our folded 
mountains cannot owe their origin to the wrinkling and shriv- . 
elling of the crust." "But the evidence of compression is so 
conspicuous and so incapable of being misread that geologists 
are not likely to give up their contraction theory. They will 
insist that physicists who speculate on the subject of crustal 
evolution must first take into consideration the actual facts of 
crustal deformation. No theory, however brilliant and plaus- 
ible, can meet with acceptance if inconsistent with the well 
ascertained results of observations." 
Prof. Geikie then passes on to consider the meteoritic 
theory of the earth, which supposes that it has gradually been 
.formed by the accretion of smaller solid masses. Quoting from 
Prof. Chamberlin (Science, June and July, 1899), he says that 
"the high internal temperature may be the sequence of an 
earth which grew up in this way with sufficient slowness to 
remain essentially solid at all stages." 
The conclusion of Prof. Geikie's paper consists of a com- 
