B. Hobson—WMevrican Volcanoes. 7 
refers to the Upper Pliocene the pumiceous tuffs and breccias of the 
Las Cruces, Monte Alto, and Sierra Nevada range (separating the 
basin of Mexico city from the valley of Puebla), and Mr. Flores states 
that these tuffs correspond to those around the Nevado de Toluca, 
but apparently Mr. Aguilera does not give his reasons for assigning 
the tutfs he mentions to the Upper Pliocene. As Cretaceous lime- 
stones underlie the voleano and Pleistocene deposits overlie the 
argillaceous tuffs, which in turn overlie the pumiceous tuffs of the 
voleano, it may be considered to be of Tertiary age, and both 
Mr. Flores and Mr. E. Ordonez believe it to have first appeared at 
the beginning of the Pliocene. No eruption is recorded as having 
occurred in historic times, and the mountain appears to have suffered 
considerable erosion. We rode down to Calimaya by a more direct 
path, and returned by train to Toluca the same evening. 
Toluca to Jorullo. 
August 23rd. We left Toluca by train for Morelia (altitude 
6,396 feet), 188 miles distant, passing on the way the saline lake 
of Cuitzeo, 45 miles long by 10 wide, but, like the rest of the 
Mexican lakes, very shallow, hardly more than 20 to 26 feet deep. 
August 24th was spent in Morelia, and on the 25th Mr. Ezequiel 
Ordoiiez, sub-director of the Mexican Geological Institute and 
Secretary of the International Congress, who was to be our guide 
to Jorullo, joined us. In the afternoon we left by train for Patzcuaro 
(alt. 7,183 feet), 39 miles away. Close to Patzcuaro is the beautiful 
lake of the same name (alt. 6,690 feet), about 123 miles long and 
23 feet in average depth. We walked from the town to the terrace 
of Los Balcones on the volcanic hill of El Calvario. From this point 
there is a splendid panorama of the lake, intersected by promontories, 
studded with islands and surrounded by basaltic cones so numerous, 
so graceful, and so perfectly preserved as to rejoice the heart of the 
geologist. 
August 26th. At 6 a.m. we started, accompanied by an escort of 
rurales, to ride to Ario, about 28 miles away. After passing through 
maize fields we rode through the most beautiful park-like scenery, the 
hills on either side being all volcanoes, often beautifully preserved 
cones and either wooded or grass-grown from foot to summit. 
Volcanoes are as plentiful in Mexico as blackberries in England. At 
8.45 a.m. we arrived at Santa Clara de Portugal, where maidenhair 
ferns grow like weeds on the old walls. On leaving it we passed 
through country which one might have mistaken for a bit of the 
English Lake, District, but no lakes were visible, and on a near view 
the vegetation differed. We arrived at Ario (alt. 6,200 feet) at 2.30. 
August 27th. We left Ario at 6 a.m. Our road was chiefly down- 
hill; we were descending the southern escarpment of the Mexican 
plateau. The vegetation became more tropical ; bananas, mimosas, and 
Opuntias were common, and small well-wooded volcanic cones were 
numerous. At 9.35 we reached Rancho Nuevo (alt. 4,593 feet), 
11 miles from Ario. We left at 12.40 and continued to descend, 
passing through a pine forest. In an hour we were among fan-palms, 
and as we reached lower levels they increased in number. Here and 
