DIRECTIONS OF VIBRATORY MOVEMENT. 309 
cal movements. In Prince Poniatowski’s house, which stands on the hills at an altitude 
of about 500 feet, a mile from the fault-line, all the windows — over 30 in number— 
were so raised. It is believed that all of the windows in this case were of the kind that 
are balanced by weights hanging within the frame. In many places on low land the same 
thing occurred. In one case a baby’s cot Jumped up and down, breaking its castors. 
Bodies frequently assumed positions such as would have been imparted by twisting 
movements. This was true in the case of many houses, turrets, articles of furniture, 
hanging pictures, and chimneys. The apparent twists were both in the positive and the 
negative direction, and varied from a few degrees to 180 degrees. In the opinion of 
the writer, such positions were the result of a complication of movements rather than of 
a twisting motion. The twisted position of furniture was often ascribable to the rolling 
of the castors. Dishes, vases, etc., could easily change their orientation, especially 
if they were tipt up, as was frequently done. But the majority of articles were caused 
to shift their position horizontally, in one or more direct lines. A large number of houses 
slid on their foundations, dishes and books slid off their shelves, and but few things 
failed to change position. 
Movement of houses. — One of the principal objects of this investigation was to find 
out in what direction houses moved on their foundations. Data were gathered concern- 
ing 842 wood, concrete, and brick foundations in regard to which it could be learned 
whether or not movement of the superstructure had taken place. Of this number 190, 
or 23 per cent, gave clear evidence of movement. In each case the direction and dis- 
tance were tabulated. The directions are given in the following table. The distances 
are given in the first table on page 365. 
Table showing direction of movements of houses on their foundations (total number of observations, 190). 




















Group 1. Group 2. Group 1. Movements in directions 
Movements Movements Movements of Groups 1 and 2 
NW. and SW. NE. and SE. N.and S. combined. 
Localities, ; 
SW. NE. NW.| W. | SW. | SW. | NW. 
NW.| W. |SW.| and|NE.| E. | SE, | and Ss. N. and | and | and | and | and 
NW. SE. NE. E. SE. | NE. | SE. 
San Mateo . 25 ae235 4) 40 4 18 Sls aero Z 4 4 = ae 2 3 5 5 
Redwood ter rch, © 8 Tie Lee LO De leat 1 2 ene eerie litre et 
Belmont, Homestead 
AMG mans OATlOS. als alee cate ol ty ee sa SE ee eS i eer, el (ee el eee | eee ee 
Burlingame and San 
Na Teorellsas ee eoremeaeye al) 2 dy wlteee era renee is Meta Roce Meas (Pe eeears 2 ao 
Hbotainia ck) seems} of |rod 44, 1D OP LOLS he 5 6 2 2 3 5 * ‘ 
Group totals ... 125 36 8 17 
— — | 
Group per cents . . 65 19 6 9 






Moved either SW. or NE., or in both directions, 31 per cent of total; moved either NW. or SE., or in 
both directions, 27 per cent of total. 
The majority of houses that shifted moved southwest and northwest, or combinations 
of these directions. The west movements tabulated in practically every case were a 
combination of movement of the house over the edge of the foundation to the northwest 
and southwest equal distances, so that the effect was the same as from a single move- 
ment west. It was not known whether there had been a single shift west, or two at 
right angles southwest and northwest. The author inclines to the belief that there 
were two main movements causing houses to shift southwest and northwest, rather than 
one in an east and west line, inasmuch as so many of the movements were simply south- 
west or northwest, or not directly west. The movements tabulated in the southwest 
and northwest column are those cases in which both movements affected the house, one 
