1 34> Dr. Wollaston's Essay on Fairy-Kings . 
in that instance, measured from them toward the centre, was 
about twelve or fourteen inches, while the mushrooms 
themselves covered an exterior ring about four or five inches 
broad. 
The position of these mushrooms led me to conjecture that 
progressive increase, from a central point, was the probable 
mode of formation of the ring. I was the more inclined to this 
hypothesis, when I found that a second species of fungus pre- 
sented a similar arrangement, with respect to the relative 
position of the ring and fungi ; for I observed, that in all in- 
stances the present appearance of fungi was upon the exterior 
border of a dark ring of grass. I thought it not improbable 
that the soil, which had once contributed to the support of 
fungi, might be so exhausted of some peculiar pabulum neces- 
sary for their production, as to be rendered incapable of pro- 
ducing a second crop of that singular class of vegetables. The 
second year's crop would consequently appear in a small ring 
surrounding the original centre of vegetation, and at every 
succeeding year the defect of nutriment on one side would 
necessarily cause the new roots to extend themselves solely 
in the opposite direction, and would occasion the circle of fungi 
continually to proceed by annual enlargement from the centre 
outwards. An appearance of luxuriance of the grass would 
follow as a natural consequence, as the soil of an interior circle 
would always be enriched by the decayed roots of fungi of the 
preceding years growth. 
By reference to Dr. Hutton's* “ Observations on certain 
natural appearances of the ground of the hill of Arthur's Seat 
near Edinburgh," we find the progressive enlargement 
* Edinburgh Transactions. 
