ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 235 
to a point south of Folsom Street; thence easterly nearly to the wharves. Between 
Washington and Sacramento Streets, this boundary is barely east of Montgomery Street. 
Immediately west of these districts, low intensity prevailed. 
It is of interest to inquire whether all or only a portion of this district in which high 
intensity was developed is ‘“‘made” land. In the map (fig. 51) is reproduced a portion 
of the U.S.C. & G.S. chart, “City of San Francisco and its Vicinity,” published in 1853 
from surveys made in 1851-1852. On it the dot-and-bar line represents the course of 
the ‘original high-water line according to plot of Wm. M. Eddy’s survey dated 1852.” 
The “‘zero contour” which determines the configuration of the shore, except where wharves 
put out, is shown by a continuous line; it is not expressly defined, but it is believed to 
represent mean low-water, as the soundings are measured from this level. It is needless 
to point out that this contour is drawn farther seaward than the original high-water line. 
The portion thus delimited has an area of not less than 20 city blocks, partly or wholly 
occupied by buildings. Quite outside the “zero contour,” as shown on this map, are 
8 complete blocks and portions of others — an area of not less than 10 city blocks, partly 
or wholly built upon. If, then, confidence may be placed in the location of the original 
high-water line of the Eddy survey of 1852, there were already in San Francisco 30 blocks 
of “‘made” land, occupied wholly or in part by buildings before the end of 1853, less than 
4 years after the sudden rush to California which followed the discovery of gold in 1849. 
The revised chart of 1857 shows that very little additional land was made in this district 
in the succeeding four years. 
Without conflicting evidence from other surveys, and no such evidence has been found, 
the high-water line established by the Eddy survey can not be discredited. Still it is 
proper to state that these facts raise some doubts as to the accuracy of its delineation, and 
that the evidence developed by the earthquake does not tend to dispel these doubts. 
The gradation in the effects produced by the shock, from great magnitude at the water- 
front to small at the former land margin, would suggest that at least the marginal dis- 
trict where only Grade C intensity was developed, tho outside the location of the original 
high-water line, might not be made land, altho it has undoubtedly been somewhat ele- 
vated by grading. Very little stress can be laid on this suggestion, however, for these 
districts suffered very severely in the earthquake shock of 1868; but the materials used 
in filling were then, of course, shaken together, and in addition, the slow settling together 
from year to year has undoubtedly compacted the earlier made land much more than that 
recently “made.” Besides, the exhibition of damage depends upon the character of 
the structures in a given locality, as well as upon the ground, and it is to be noted that the 
buildings along Kearney, Montgomery, and Sansome Streets comprized a larger per- 
centage of excellent structures than the streets nearer the wharves. The problem is thus 
complex, and very likely unsolvable; but there remains the haunting suggestion that the 
“original high-water line” does not constitute the landward boundary of the “made”’ 
land, properly speaking. At any rate, it is very clear that that which was known to be 
“made” land suffered much more severely than that which was known to be natural 
alluvium. 
It is important to recognize that, despite the great intensity manifested near the water- 
front, first-class modern buildings, such as the Ferry Building, built upon deep piling 
or grillage foundations, were not imperiled by injuries to their walls or framework. 
Some rivets were sheared off; some tension rods were stretched; an occasional girder 
was dislodged, and cracks were formed here and there in the brick and stone walls. 
Large financial loss was unquestionably occasioned, but buildings of this type were not 
in serious danger of collapse nor of being toppled over, either during or after the shock. 
Nevertheless conservative engineers recognize that even these structures were weakened. 
They recognize, too, that future shocks may exert greater energy, and they are trying 
to devise buildings better able to resist the peculiar stresses of earthquake shocks. ‘The 
