DIRECTIONS OF VIBRATORY MOVEMENT. 361 
It will be seen from the preceding table that out of a total of 922 brick-chimneys that 
fell, 60 per cent went down the roof, while only 3 per cent fell in the opposite direction : 
22 per cent fell obliquely, and 3 per cent with a leap apparently regardless of the roof. 
The predominance of the northwest and southwest directions, however, does not seem 
to be wholly due to the roof-slope. The table shows that in each division the north- 
west-southeast and northeast-southwest directions of movement are in the majority, 
even tho the chimneys have fallen in a direction contrary to the slope of the roof. 
The evidence here is not of the best, but there certainly seems to be a tendency toward 
motion in the same directions as those dominant in the case of the houses themselves. 
It may be supposed that chimneys fell in those directions owing to the movement of the 
house, but the majority of chimneys falling came from houses that were not dislocated. 
The evidence of the chimneys falling obliquely, up the roof, shifting, and jumping 
was the best, since they moved without regard or in opposition to structural influence. 
Among these much the largest number of movements in any two directions were north- 
west and southwest, and the next largest number just opposite. The northwest-south- 
east and southwest-northeast movements, then, were in the majority, making a total 
of 41 per cent, while a majority of those remaining moved in directions intermediate. 
Movement of dishes, books, etc. —Such loose articles as books, dishes, bric-d-brac, 
and lamps are, as a rule, free to fall or slide as they will, but in this region, especially 
in the town of San Mateo, the shelves on which many of them stood faced northwest, 
southwest, northeast, and southeast. The possible directions for falling in such cases 
were limited and this detracts somewhat from the value of the figures in the table. 
Table showing percentage of directions in which dishes moved. 

Direction. | Per cent moved, by directions. || Direction. | Per cent moved, by directions. 




Nw. 22 W. 4 
SW. 27 49 3 ., 3} 7 
NE. 20 A N. 1.5) ; 
SE. 20 S. 25 5 




SW. to NE., 47 per cent; NW. to SE., 42 per cent. 
Of objects overthrown, 89 per cent fell in one of these four directions. Tho many of 
the movements were determined solely by the direction in which the shelves faced, still 
the small number of movements in intermediate directions favors the idea that north- 
west and southwest and opposite movements predominate, for many of the cases recorded 
were of articles free to fall in any way whatsoever, and others were of articles that slid 
some distance along shelves without falling off. The east and west movements were 
more important than those north and south, showing a tendency in that way. 
As to the cases in which dishes remained in position without appreciable shift on 
shelves facing in the four main directions of movement, the southwest-facing shelves 
were most of them left empty, and there was a much greater number of cases in which 
dishes remained stationary when it seemed natural for them to fall northwest, northeast, 
or southeast. 
The case of a town library is especially worthy of mention: of books facing southeast, 
none fell; of those facing northwest, a few fell; of those facing southwest, all fell. 
Movement of furniture, etc. —These data include facts concerning the direction of 
movement of pianos, stoves, tables, bookcases, beds, bureaus, counters, cases, mantel- 
pieces, safes, deposits of merchandise, and the like. These were generally free to move 
in all or most directions. The way in which the furniture was moved was learned at 
every house, and the results tabulated by regarding every direction of movement in 
any one house as a unit. Hach unit, or case of movement, therefore, usually represents 
several individual movements. 
