216 Influence of Agricvlture on Health. 
largements never fail to rise to the top of the highest water 
level, and must, in some instances, attain an elevation of at least 
twenty-five feet; so that when the knees are no longer available, 
the same kind of structure is continued up the body of the tree 
to where they come in contact with the atmosphere. 
One specimen somewhat over seventeen inches, was found to 
contain three hundred and eighty annual layers, varying in thick- 
ness from the x'oth part to the ^th of an inch. In a tree of not 
more than forty-two inches, we counted over sixteen hundred 
rings of growth; they decreased in thickness on receding from 
the centre, until one inch contained not less than ninety-five. 
From all this it may be safely presumed that there are cypress 
trees in the forests numbering over two thousand years. — Silli- 
man's Journal. 
INFLUENCE OF AGRICULTURE ON HEALTH. 
The following is an extract from a paper read before the New 
York State Medical Society, Feb. 1, 1848, by Alexander Thomp- 
son, M.D.: 
Agriculture has effected great changes in the physical condi- 
tion of the earth, by displacing the forests, draining the fens and 
marshes, removing obstructions from water courses, reclaiming 
lands from the overflow of rivers, and the encroachments of the 
sea; exposing animal, vegetable and mineral substances to the 
decomposing action of the atmosphere; subduing, ameliorating 
and preparing the soil for the reception of various vegetable pro- 
ductions. Powerful causes are thus at work for affecting the hy- 
genic condition of nations. Countries scourged and depopulated 
by devastating diseases, are rendered habitable; and the subtle 
poison of the destroying miasma, is disarmed of its power. 
No fact, perhaps, is better established, than that by the opera- 
tions of husbandry the healthful condition of countries is improv- 
ed, inasmuch as in the very success of these operations consists 
the removal of those causes so potent in generating disease. The 
Pontine marshes were once as celebrated for the salubrity of their 
atmosphere, as they are now for their deadly emanations. Wealth 
and refinement, and taste, expending all their resources, had con- 
verted this region, inexhaustible in its treasures of line climate 
and productive soil, into the most favored spot of the then known 
world. Its sunny slopes and fertile plains were covered with the 
villas, and farms, and gardens, and pleasure grounds, of the 
wealthy and luxurious Romans. 
