BULLETIN OF THE BUSSEY INSTITUTION. 13 
true that the beneficial influence of rocks rich in potash, like several 
of the granites mentioned above, may sometimes be plainly seen in 
the luxuriant vegetation upon patches of soil at the bases of ledges of 
such rocks, or in hollows among the rocks upon which the products 
of their disintegration have fallen, or whither they have been washed 
by rains. In the vicinity of Gloucester, at Cape Ann, I have myself 
noticed not a few cultivated fields and many small patches of pasture 
grass whose luxuriance was clearly to be ascribed to supplies of food 
afforded by the crumbling granite of the immediate vicinity.* 
The good effects produced by such rocks must manifestly often be 
hastened and increased by the method of cultivation, so common 
among us, in which brush-burning finds place, since the surfaces of the 
rocks are much broken and crumbled by the action of fire. 
It would be interesting to observe in many localities, what rocks 
seem to nourish the neighboring vegetation through the products of 
their decay, and to note whether the soils that result from the decay 
of such rocks derive any peculiar benefit from the application of spe- 
* Since the above was written, I notice that attention has already been 
called to these appearances in the neighboring locality of Marblehead, by Mr. 
J.J. H. Gregory of that town, in a striking paragraph which I copy from the 
“Transactions of the Massachusetts Society for Promoting Agriculture,” New 
Series, vol. i. pt. 3, p. 351. 
_ “Formed for the most part from the decomposition of her primitive rocks, the 
soil of Marblehead, though scanty, is proverbially strong, covering our pasture 
lands, that have been closely fed over a century and a quarter without any cultiva- 
tion or manuring, with a carpet of white clover during the rainy season. The soil 
of our islands is so amazingly productive of the grasses as to set all the attempts 
of the chemist to explain the fact from the chemical composition of the soil at 
defiance ; no one can realize it until he has visited them during the growing 
season (Baker’s Island is an instance), and I challenge any one to explain it by 
any theory that does not ascribe an influence far greater than has heretofore 
been customary to the qualities communicated to the air from the surrounding 
ocean.” 
With regard to the last part of Mr. Gregory’s statement, it should be said 
that the explanation of the influence of sea-air upon the fertility of granitic 
soils is really not far to seek. The matter is readily explained, in good part, 
if not entirely, by a reference to the familiar facts that fields near the sea are 
kept moist well-nigh continuously by fogs and mists as well as rains, during 
the growing season; that the air near the sea is, comparatively speaking, highly 
charged with particles of salt, and that salt when absorbed by the soil has the 
power of liberating potash from some of its combinations in such manner that 
plants can freely feed upon it, as was discovered in 1850 by Professor Way, 
and as has been clearly described by Professor Johnson, in his ‘‘ How Crops 
Grow,” New York, 1870, p. 836. 
