20 
CLIMATIC CHANGE. 
Even if we suppose an identity of species, of race, and of 
habit to be established between a given ancient and modern 
plant, the negative fact that the latter will not grow now 
where it flourished two thousand years ago does not in all 
cases prove a change of climate. The same result might 
follow from the exhaustion of the soil,* or from a change in 
the quantity of moisture it habitually contains. After a dis¬ 
trict of country has been completely or even partially cleared 
of its forest growth, and brought under cultivation, the drying 
of the soil, under favorable circumstances, goes on for genera¬ 
tions, perhaps for ages.f In other cases, from injudicious 
the ears of this grain found in old Peruvian tombs belong to varieties not 
now known in Peru.— Travels in Peru , chap. vii. 
* The cultivation of madder is said to have been introduced into Europe 
by an Oriental in the year 1765, and it was first planted in the neighbor¬ 
hood of Avignon. Of course, it has been grown in that district for less 
than a century; but upon soils where it has been a frequent crop, it is 
already losing much of its coloring properties.— Lavergne, Economic Pu- 
rale de la France , pp. 259-291. 
I believe there is no doubt that the cultivation of madder in the vicinity 
of Avignon is of recent introduction ; but it appears from Puller and other 
evidence, that this plant was grown in Europe before the middle of the 
seventeenth century. The madder brought to France from Persia may be 
of a different species, or, at least, variety. “ Some two years since,” says 
Fuller, “madder was sown by Sir Nicholas Crispe at Debtford, and I hope 
will have good success ; first because it groweth in Zeland in the same (if 
not a more northern) latitude. Secondly, because wild madder grows here 
in abundance ; and why may not tame madder if cicurated by art. 
Lastly, because as good as any grew some thirty years since at Barn-Elms, 
in Surrey, though it quit not cost through some error in the first planter 
thereof, which now we hope will be rectified.”— Fuller, Worthies of Eng¬ 
land, ii, pp. 57, 58. 
Perhaps the recent diseases of the olive, the vine, and the silkworm— 
the prevailing malady of which insect is supposed by some to be the effect 
of an incipient decay of the mulberry tree—may be, in part, due to 
changes produced in the character of the soil by exhaustion through long 
cultivation. 
t In many parts of New England there are tracts, miles in extent, and 
presenting all varieties of surface and exposure, which were partially cleared 
sixty or seventy years ago, and wTiere little or no change in the proportion 
of cultivated ground, pasturage, and woodland has taken place since. In 
