ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 205 
According to the record of Matthes and Holway, similar cracks appear in the same line 
4 miles and 9 miles north of Petaluma, and there seem to be other breaks on the way toward 
Point Delgada. It seems certain that this first crack is an earthquake rift, and that the 
disturbances at Santa Rosa and Sebastopol are due to this and not to the main Rift which 
lies parallel to it to the west. 
Mr. G. K. Gilbert also visited the Burbank farm at Sebastopol, and contributes the 
following note referring in part to the cracks discust by President Jordan: 
Mr. Luther Burbank gave mean account of personal experiences and of various phenomena 
at Santa Rosa, and I record such items as are supplementary to Professor Holway’s report. 
Mr. Burbank was awake at the time. He immediately got out of bed, but found he could 
not stand, and settled back against the bed, holding on to the window casing and bedpost. 
The initial impulse was from the west, and during the first portion of the earthquake the 
motion was oscillatory, east and west. Then it became oscillatory north and south, and 
at the close there was a complex motion which he compared with that of a vessel in a choppy 
sea. From the window he saw trees waving, and after the tremor had ceased he seemed to 
see a continued disturbance in the foot-hills at the east, as tho the tremor was retreating in 
that direction. He said that practically every one in Santa Rosa who was on foot at the 
time was thrown to the ground, but that men on bicycles were not upset. During more 
than 30 years’ residence in Santa Rosa he had felt about 130 earthquakes. None were 
comparable in violence with the recent one, tho several had broken chimneys. A number 
of earthquakes which were felt generally in Santa Rosa had not been felt at all in Sebastopol, 
and he thought that Santa Rosa was peculiarly subject to shocks. 
A shock was felt in Santa Rosa on April 17, 1906. 
Mr. Lawrence, foreman on Mr. Burbank’s farm at Sebastopol, stated that men standing 
or walking at the time of the shock were thrown from their feet, as were cows and horses. 
The small house on the Burbank place was moved from its foundations a few inches down- 
hill, and Mr. Lawrence mentioned a number of houses which had moved various distances, 
the direction in every case being downhill. On the Burbank farm a small landslide occurred, 
a layer of moist soil only a few feet in thickness moving down the slope, introducing bends 
in various lines of cultivated plants. I saw another feature of this sort on an adjacent farm, 
and was told of others which I did not visit. 
In a general note on the intensity of the earthquake, appended to detailed observations 
which have been incorporated in the foregoing account of the distribution of intensity, 
Mr. G. K. Gilbert says: 
In general the violence seems to have been less in Petaluma than in Sebastopol, Santa 
Rosa, or Maacama, notwithstanding the fact that it is nearer the main fault. As compared 
with Sebastopol and Santa Rosa, however, Petaluma seems to be on relatively firm ground, 
excepting a small district bordering the marshes. In a general way, I think the relative 
violence in the three towns corresponds to the character of their foundations, but consider- 
ing the district as a whole, in relation to districts nearer the main fault, it is clear that the 
intensity was exceptionally high. 
Altruria, Sonoma County (R. 8. Holway). — About 5 miles north of Santa Rosa, at 
Altruria, cracks are said to have opened in the road, and springs to have flowed for a 
short time. There was no indication of either last May. 
Mark West Springs (R. 8. Holway).— The concrete walls of several springs were 
cracked and damaged. Chimneys fell on the house. The springs are reported as flow- 
ing much more freely, and the temperature of two of them is said to be very much higher 
than before the earthquake. They are now quite warm to the hand, and it is said that 
they were formerly cold. I could get no reliable information as to temperatures, as no 
records were kept. The increased flow is independently indicated by circumstantial 
evidence. 
Windsor. Population 130. (R. 8. Holway.) — Here 2 or 3 brick buildings were badly 
wrecked, and the water-tank at the railway station was overthrown. The cemetery 
