i 
: 1887] Geology and Palæontology. : 1105 
quent intervals by many lesser movements in the next three 
- days, and less frequently at least up to May 29. In this part of 
Arizona solid house-walls, of adode, or unburned brick, were 
“cracked or overturned, while huge rocks in the steep mountain 
gorges rolled down, causing much damage. Fires, perhaps 
kindled by these in their course, appeared immediately after- 
wards in various wooded regions in Sonora and Arizona, 
giving rise to many false rumors of volcanic eruptions. The 
movement here seemed from south to north; the Sonora railroad 
f was nearly destroyed, many people being killed and wounded. 
} Opoto suffered in a similar way, and Fronteras to a less extent. 
} The district chiefly affected by the earthquake is, however, for 
€ most part a desert, with some cattle-ranches and mining 
stations. 
Interesting studies were made by the authors in the valleys, 
or mesas, between the parallel mountain ridges in this region, 
both in the San Pedro and Sulphur Spring Valleys. The latter, 
f several hundred feet, 
uth course, verti- 
Case 
eas evidently connected with outbursts 
which, along cracks,—marked by depressions on 
ometimes covered areas of many hundred 
Ographs, which were exhibited. They 
