BEHAVIOR OF INDIVIDUAL STRUCTURES. 107 
is ordinarily done. In fact, if the diagonal is to be fastened directly 
to the wind strut, there should be a connection between the strut and 
the column capable of taking up the horizontal component of the 
stress in the diagonals. Knee braces, such as those used in the Call 
Building, possess a manifest superiority over ordinary bracket seats 
in construction of this sort. An examination of the condition of the 
bracing in the ferry-building tower can leave no doubt whatever 
that the tower was just on the point of total collapse. Conditions 
were so bad that the superintendent of the contracting firm that 
was taking the masonry down evidently felt, a little uneasy about 
what would happen when the masonry covering was removed from 
the portion of the steel work where the bracing was most seriously 
damaged. He was proceeding with great judgment and caution, 
however, and no doubt succeeded not only in removing the damaged 
masonry with safety, but in so tying together the steel work as to 
avoid all danger of collapse. 
A part of the masonry in the east front of the tow T er was precipi- 
tated from its position (PL XL VI, A) and fell through the sky- 
light and onto the floor of the corridor in the upper story of the 
main building. This floor consisted of stone concrete, reenforced 
with expanded metal, and carried by steel beams with spans appar- 
ently of 7 or 8 feet. The contractor's superintendent, already men- 
tioned, told me that he thought the amount of masonry so precipi- 
tated on this floor amounted to 30 or 40 tons. It punched in the 
floor one small hole not much larger than a man's fist, but nothing of 
any size got through. It is doubtful whether any form of floor 
arch or slab except reenforced concrete and possibly solid brick 
would have stood this test so successfully. Certainly no hollow-tile 
floor such as those in ordinary use would have stood it for a moment; 
the falling mass would have gone on through to the ground. 
Along the west front of the ferry building, about halfway up the 
second-story window piers, most of the stonework had slipped about 
an inch. Some of the first-story piers were so badly shattered by the 
earthquake that they had to be boxed in to prevent the loose stone 
from falling. There were in the floor construction of the tower and 
of the building proper a few r cracks which I thought might be due 
to the earthquake, although it is possible that they may have been 
shrinkage cracks. I was not able to get any convincing testimony 
on this point, but I have seen a good many shrinkage cracks and am 
of the opinion that most of these cracks were due to the earthquake 
and not to shrinkage. On the whole, the ferry building stood the 
shock remarkably well. It would seem to be the part of wisdom, 
however, to tear the tower down altogether and not to rebuild it. 
