June 15, 1906.] 



SCIENCE. 



917 



At a special meeting on the evening of May 

 18, the following illustrated papers were pre- 

 sented : 



Epitome of the Geologic History of the Cali- 

 fornia, Coast Ranges: Mr. F. L. Eansome. 

 Evidence of Geologically Recent Movements 



near San Francisco: Mr. Geo. H. Ashley. 

 Location and Character of the Faults in the 



Earthquake Region: Mr. Ralph Arnold. 



Lantern views showing some efEects of the 

 earthquake: These views, sent by Messrs. G. 

 K. Gilbert and W. C. Mendenhall, were ex- 

 hibited by Mr. Ashley. 

 Seismograph and Magnetograph Records of 



the San Francisco Earthquake: Mr. L. A. 



Bauer. 

 Comparative Intensities of the New Madrid, 



Cha/rleston and San Francisco Earthquakes : 



Mr. M. L. Fuller. 



While all conclusions regarding the San 

 Francisco shock must necessarily be pro- 

 visional until the publication of accurate 

 scientific data, sufficient evidence is at hand 

 to warrent certain general conclusions as to its 

 intensity as compared with the New Madrid 

 earthquake which shook the Mississippi Val- 

 ley in 1811-12 and the Charleston disturb- 

 ance of 1886. Considering first the area af- 

 fected by Assuring, we find such phenomena 

 have been reported to extend at least 125 

 miles both north and south of San Francisco 

 and throughout a belt 50 miles wide. At 

 New Madrid the length of the disturbed area 

 was 110 miles and the width about 60 miles, 

 while at Charleston it was only 30 miles long 

 and 20 miles broad. It should be noted, how- 

 ever, that at San Francisco the fissuring oc- 

 curred only at widely separated points where 

 the conditions were peculiarly favorable, 

 while in the New Madrid and Charleston 

 areas the entire surface within the limits 

 mentioned was affected. 



The main San Francisco shocks appear to 

 have lasted only about one and one-fourth 

 minutes, with slighter tremors for a few hours 

 and occasional light shocks for several days. 

 At Charleston the severe tremors were like- 

 wise confined to a few hours, but at New 

 Madrid they continued at short intervals for 



over a year, nearly 2,000 shocks, 53 of which 

 were severe, occurring in the first three 

 months. The effect on buildings was also 

 greatest at New Madrid, even low cabins being 

 shaken down, but at Charleston relatively few 

 of even the larger buildings were destroyed 

 although many were injured. The destruction 

 at San Francisco was somewhat greater, but 

 the better class of buildings, especially the 

 steel structures, generally escaped. The mag- 

 nitude of the surface undulations was greater 

 at Charleston than at San Francisco and 

 greatest of all at New Madrid, in which re- 

 gion considerable areas of forest were thrown 

 down even on the level ground, while the blufl^s 

 were literally shaken to pieces, the resulting 

 landslides converting them into jumbles of 

 earth heaps and tree trunks for a distance of 

 100 miles. Such landslides were absent at 

 Charleston, but occurred occasionally at San 

 Francisco, although much less frequent and 

 conspicuous than at New Madrid. 



Tidal waves were practicajly absent both at 

 San Francisco and at Charleston, but at New 

 Madrid the Mississippi was disturbed by great 

 waves which destroyed much of the shipping 

 and the current even retrogressed in certain 

 localities. Cracks and craterlets, with pos- 

 sibly one or two exceptions, seem to have been 

 absent in the San Francisco region, but were 

 common at Charleston and New Madrid. In 

 the former locality the cracks were usually less 

 than an inch across, but in the latter were 

 often many feet in diameter. Craterlets 

 abounded in both localities, but both in the 

 area covered and in number and amount of 

 sand and water extruded. New Madrid stands 

 first. The courses of the streams were little 

 affected at San Francisco or Charleston, but 

 in the New Madrid area the courses of many 

 were changed, the water following new cracks 

 instead of the old channels. Others were de- 

 flected by the warping of the surface, while 

 still others were obstructed by faults or sharp 

 folds giving rise to extensive marshes or large 

 lakes of open water. In fact the New Madrid 

 area seems to be the only one of the three in 

 which the general level of the land was notably 

 affected. 



