160 MR GOODCHILD. 
It is perhaps not difficult to extend the idea which the 
foregoing paragraph is intended to elucidate in such a man- 
ner that it should apply to the severance of any loosely- 
attached material from the ceiling of a room, from the walls, 
from the floor, or even from all three surfaces. It is only 
necessary that they should have been originally all coated 
with the saine material, and that they should be all acted 
upon by the same impulse from without. If that idea is 
properly grasped, we may now proceed to apply it to the 
case specially under consideration. 
The ingress of the solutions containing what is to become 
Chalcedony seem to have taken place under an impulse of 
a mechanical nature. As a result of this it has often 
happened that parts of the earlier-formed layers, including 
those of the Green Earth, have been detached and thrust 
inward. When the ruder impulse has moderated down, 
deposition of Chalcedony has gone on over the whole inner 
surface, and equally over the rags and tattered shreds of 
the green priming as over the other parts of the cavity. 
Little by little all these irregularities have been smoothed 
over by the deposits of Chalcedony, which envelops the 
torn and ragged shreds of Green Earth in much the same 
manner as amber surrounds and encloses the flies. By this 
means some of the most beautiful and striking features of 
agates are produced. Joss Agates are nothing more than 
chalcedonic agates which enclose shreds and frayed-out rags 
of Green Earth, whose resemblance to moss is merely of 
a superficial nature, and is quite fortuitous, for in the great. 
majority of cases the tattered shreds of Green Earth take 
forms which bear little or no resemblance to the forms of 
vegetable life from which the Moss Agates derive their 
popular name. It will be noted that true Moss Agates are 
formed at an early stage in the growth of an agate, in which 
respect they differ from Mochas, to be noticed presently. 
In other cases the deposition of Chalcedony has taken 
place at a rate somewhat above the average, and then very 
much the same kind of result has been caused as would 
ensue if the leak in the roof, so often referred to, allowed 
more rain-water to come in than just sufficed to keep the 
ceiling moist. In this latter case, as we all know, the 
