14 PHYSICAL FEATURES ETC. 
MEXICO. 
The general aspect of the Mexican plateau, as far south as the City of Mexico, has 
been previously alluded to in the account of my journey there in 1887-1888 (antea, 
pp. 9, 10). On each coast, between the mountain ranges and the sea, there is a com- 
paratively narrow strip of low land, producing a tropical vegetation, which on the 
Atlantic extends a little to the north of Tam pico, where the forests with epiphytical 
orchids suddenly disappear; while on the Pacific the low land terminates a little above 
Mazatlan, where the coco-palm ceases to grow, but the vegetation generally is less 
luxuriant on this coast than on the Atlantic. The plateau itself is arid in consequence 
of the rainfall being precipitated on the two coastal ranges, and produces but a scanty 
vegetation, consisting chiefly of Yuccas, Agaves and Cactacee, and Mesquite (Prosopis). 
The margins of the few existing streams or pools produce a few scattered willows and 
poplars, and the whole country presents a desolate appearance. ‘The plateau is indeed 
a continuation of that of Arizona and New Mexico, and though it is depressed in the 
valley of the Rio Grande at. El Paso, where the railway crosses, it is still at an altitude 
of 3700 feet above the sea. Southward it mounts considerably higher, and on 
reaching Zacatecas, the highest point on the railway leading to the Capital, there 
is an elevation of 8000 feet. The City of Mexico is situated in a valley surrounded by 
ranges of hills clothed towards their summits with pine trees, and reaching an elevation 
of about 10,000 feet, while to the south-east are the two lofty volcanoes of Popo- 
catepetl and Ixtaccihuatl, the tops of which reach above the snow limit. Numerous 
streams descend from the mountains and empty themselves into an alluvial valley with 
swampy meadows and form several large lakes, of which Texcoco, Chalco, and 
Xochimilco are the most important. It was on Texcoco that the old Aztec Capital 
was situated; the houses were built on piles, and the city, which was approached by 
a causeway, was destroyed by Cortes at the time of the Spanish conquest in 1519— 
1621. The modern town was placed by the conquerors on the swampy ground about 
two miles from the eastern margin of the lake, but notwithstanding the altitude it 
became one of the most unhealthy capitals in the world, for owing to the frequent 
rising of the level of the lake, the town was constantly inundated. Eventually a great 
drainage scheme was inaugurated, and for 150 years vast numbers of natives were 
employed in cutting a huge dyke for the purpose of draining the overflow of the lake : 
but the sodden ground had become so impregnated with sewage that the mortality 
was still extremely high, and it was not till 1900 that President Diaz finally completed 
the extensive drainage system which now renders the city a comparatively healthy 
resort. ‘There can be but little doubt that in former times one large piece of water 
covered the whole area of the three lakes, and a map published about 1628 shows 
Chalco united with Texcoco, when the surface of the two lakes was far greater 
than it is at present. Owing to the drainage system so recently completed, there are 
