53 
_ amination of the vegetation determines this fact with absolute cer- 
_ tainty which will be shown later by diagrams. common error 
_ into which many have fallen, has led to a serious misconception of 
_ life zones by the failure to recognize the effect of humidity on the ~ 
_ climate. Hitherto the Tropical life zone has generally been sup- 
- posed to be confined to that portion of the earth’s surface bound- 
ed by the Tropics of Capricorn and Cancer and confined to the 
humid portion, but a moment’s thought will show that the arid 
portion belongs equally with the humid, though its flora is al- 
most totally different from that of the humid. This fast is also 
cstablished by the knowledge that you can grow the date paim. 
oranges and lemons, pomegranates and figs in the arid rezions by 
simply supplying the necessary moisture artificially. This there- 
fore establishes the fact that the climate of Arizona and southern 
California is truly tropical and that we must not bound the Tropt- 
cal life zone by the Tropic of Cancer, for that flora extends much 
farther north. : 
In 1883 in the Western Galaxy, the writer published an ac- 
count of the origin of the flora of the Great Basin, giving in other 
words a general summary of the facts here noted, but claiming no 
originality for these ideas because as a schoolboy, about 1860, he 
had studied in Cornell’s Geography, these same facts, though he 
had never had an opportunity to verify them himself till in 1878 
when he had stood on the loftv mountains of Colorado and had 
been profoundly impressed with the same thoughts experienced by 
Humboldt a century before. 
In 1884 a young man in the employ of the Government, Dr. 
C. Hart Merriam, who was studying the animal life of the San 
Francisco mountains in Arizona, stood on the lofty San Francisco 
peak and according to his own statement to me, saw for t é rst 
time this magnificent parorama before him and had impressed up- 
on his mind also, most forcibly, the subject of life zones, and so he 
proceeded later on to elaborate the life zones and give them pret 
of his own, ignoring the work of Humboldt and all his predeces- 
sors. He classifies the life of our western region as ne 
which he divides into Upper and Lower, Transition, and Reine 
His classification is most remarkable in the manner in sor it 
ignores hotanical facts. It was confessedly based on the it 
bution of animal life, but without knowing much 0 gids “Peas 
about the vegetable life, he states that the botanical and zoolog- 
ical life zones are identical. Whether his z00 
