10 _ B. Hobson—Mexican Volcanoes. 
curiously enough, all the watercourses are omitted). According to 
his map and description Jorullo gave rise to four lava-streams, which 
Ordonez calls ‘malpays,’ literally ‘bad lands.’ 'Yhe first and oldest 
of these was the most extensive, and each succeeding one was of less 
extent. The first flow was the first feature to be formed after the 
opening of the vent or vents, and like the second flow probably issued 
from the western foot of the Higuera plateau. It covered an area 
about 8,280 yards long by 38,060 yards broad, or approximately 
3% square miles. The second flow covered a little more than half the 
area of the first, and in most places overlies its predecessor. The 
margin of the second flow forms a kind of wall 130 to 160 feet high. 
Ordonez holds that not until these two flows had taken place did the 
vents enter on an explosive phase and form the four cones which we 
now see. The last two of the four lava-flows took place exclusively 
from the main cone of Jorullo itself by the breach already mentioned. 
Looking down upon lava-stream No. iii from the summit of the cone, 
we could clearly distinguish its margins and its black surface, and even 
trace the curves of flow of its surface, their convexity facing down- 
stream and outlined by green lines of vegetation growing on it. The 
fourth and last of the lava-streams is so fresh and devoid of vegetation 
that I think personally, it must be much later in date than the first. 
Its surface is not ropy, but exceedingly rough, scoriaceous, and of the 
‘aa’ type of the Hawaiian volcanoes. Just outside the crater, the 
upper surface of the stream having solidified, while the still liquid 
lava within flowed on, a tunnel was formed in the lava, the roof of 
which ultimately collapsed and left a channel full of débris about 
1,640 yards long, about 280 to 330 feet wide, with walls 16 to 
33 feet high. ‘This is called the ‘‘ Calle de las Ruinas” or ‘“ Street 
of Ruins.” 
As already mentioned the latest lava-stream forms a prominent 
ridge, and its sides, far from lying in or accommodating themselves 
to a pre-existing valley, rise with almost wall-like precipitous 
steepness from the surface of the cone. Another noteworthy point, — 
well shown on the map of Orddiiez, is the fact that all the lava- 
streams have flowed to the west or north and not to the east (except 
a portion of the latest stream). This westerly flow is due to the 
westward slope of the plateau of Higuera. Several fumaroles, which 
at present give off only steam at a temperature of 75° C., occur in the 
crater and on the latest lava-flow, and Ordonez found a temperature 
of 165° C. at a depth of 1 metre in a fumarole on the last lava-flow. 
The Voleancitos and Volcanic Bombs. 
From the crater rim of Jorullo the voleancitos are well seen. Like 
the main cone, the volcancitos are composed of lapilli from the size of 
a nut to that of a fist, and like it too are clothed with verdure from 
base to summit. The Volcancito del Norte is about 1,500 yards 
north - east of the main cone, rises to 3,903 feet, or 377 feet 
above its eastern base (the plateau of Higuera); the Volcancito de 
Enmedio (middle cone) lies about 1,500 yards south-west of 
the main cone, rises to 3,411 feet, or 180 feet above its eastern 
base ; while the Volcancito del Sur (southern cone), about a mile 
