712 REPORT— 1887. 



admixture with water. Thisbeinpr the case, it is pointed out that a mass of heated 

 rock may become liquefied not only bv a rise in temperature, but by the absorption 

 of water into it. Certain facts are described which seem to iudicate that tlie 

 latest ejecta of Krakatoa were formed in this way from the older lavas of the 

 same composition constituting; the lower and older part of the volcano.' 



3. Itejiort on the Volcanic Flienomena of Vesuvius and its neighhourhood. 

 See Reports, p. 226. 



4. Seventh Hejport on tlie Volcanic Phenomena of Japan. — See Reports, 



p. 212. 



5. The Sonora Earthquake of May 3, 1887. 

 JBy T. Sterrt Hunt, LL.D., F.B.S., and James Douglas, M.A. 



On the afternoon of May 3, 1887, at 2.12 Pacific time ( = 120° W. of Green- 

 wich), the first of a series of earthqualie movements was felt in the State of Sonora 

 and the adjacent parts of Mexico and the United States, over an area extending 

 from El Paso in Texas on the east, to the river Colorado and the Gidf of California 

 on the west, and from the State of Sinoloa on the south as far north as Albu- 

 querque in New Mexico ; the extremes in both directions beinof over 600 miles. 

 It was the fortune of the writers to be at the time at the great copper-mininp; 

 camp of Bisbee in Arizona, in a narrow gorge of the Mule Pass INIountains, about 

 5, -300 feet above the sea, and near the border of Sonora. A violent tremor of the 

 earth, including two sharp shocks, and lasting over ninety seconds, was succeeded 

 at frequent intervals by many slighter movements in the next three days, and less 

 frequently at least up to May 29. In this part of Arizona solid house-walls, of 

 adobe or uuburned briclc, 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 afterwards in various wooded regions 

 in Sonora and Arizona, giving rise to many false rumours of volcanic eruptions. 

 The movement here seemed from south to north ; the Sonora railroad track in one 

 place near the frontier, running east and west, was displaced Ihree inches to the 

 north ; while a chimney shaft, without being overturned, was turned violently 

 around upon its base. The small town of Bavispe in the Sierra Madre, in Sonora, 

 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 the most part a desert, with some cattle ranches 

 and mining stations. 



Interesting studies were made by the authors in the valleys, or mems, between 

 the parallel mountain ridges in this region, both in the San Pedro and Sulphur 

 Spring Valleys. The latter, hing to the east of Bisbee, and stretching north and 

 south about one hundred miles, is often eight or ten miles wide, and has its lower 

 portion in Sonora. Though without a visible water-course, water is there 

 generally fovmd at depths of from ten to forty feet in the numerous wells sunk at 

 intervals to supply the needs of large herds of cattle. As described by many 

 observers, the surface of this plain was visibly agitated by the first earthquake 

 shock, so that persons were in some places thrown down by the heaving of the 

 soil, which burst open with discharges of water, while the wells overflowed and 

 were partially filled with sand. In the southern part of this valley, for about 

 seven miles south from the Mexican frontier, the authors found the results of the 

 undulatory movement of the soil apparent in great numbers of cracks and dislo- 

 cations. For distances of several hundred feet, along some lines with a generally 

 north and south course, vertical downthrows on one side of from one foot to two 

 feet and more were seen, the depressed portion rising either gradually or by a 



' See Kralatoa Bepmi: of Boyal Soc. Com. and Geol. Mag. 1888. 



