Dec. 11th, 4h.—A shock was felt in San Francisco and at the Mission Dolores; at the latter place it is represented as being quite severe.
The whole number of which I have a record for 1855, amounts to twelve only; but there may be others which have escaped my notice on account of absence from the city.
The following table will show the number of shocks for each year, and each month of the year, for six years from 1850 to 1855, inclusive.
| 1850 | 1851 | 1852 | 1853 | 1854 | 1855 | No. for each month in six years. | |
|---|---|---|---|---|---|---|---|
| January, | — | — | — | 2 | 1 | 2 | 5 |
| February, | — | — | — | 1 | — | 1 | 2 |
| March, | 1 | — | — | 1 | 2 | — | 4 |
| April, | — | — | — | 2 | 1 | 1 | 4 |
| May, | 1 | 3 | — | — | 2 | — | 6 |
| June, | 1 | 1 | — | 1 | 1 | 1 | 5 |
| July, | — | — | — | 1 | 2 | 1 | 3 |
| August, | 1 | — | — | — | — | 1 | 2 |
| September, | 1 | — | — | 1 | 1 | — | 3 |
| October, | — | — | — | 2 | 2 | 2 | 6 |
| November, | — | — | 11 | 2 | — | — | 13 |
| December, | — | 2 | 1 | 2 | — | 2 | 8 |
| Total each year, | 5 | 6 | 12 | 14 | 12 | 11 | = 59 |
From the above it will be seen that of the total number of shocks in six years in this State, forty-eight have occurred during the spring, summer, and autumn months, and eleven during the winter months.
Of the total number noted, twenty-seven have occurred from San Luis Obispo south, and of the thirty-two remaining, nine have been felt in San Francisco at the same time they were observed at San Luis Obispo, while the remaining twenty-three were felt at San Francisco and north of that point.
Notwithstanding we have had, what may, perhaps, be considered a frequency in the recurrence of these phenomena, still there are but a very few of the total number that would merit a moment’s consideration south of the twenty-fifth parallel of north latitude, for there they would be regarded as minor affairs entirely.
From all the facts in our possession relating to the phenomena on our coast, it appears that the greatest preponderance in action and severity of effects, is exerted, for the most part, south of Point Conception, for, from this place, east, south and north, to near the Colorado, the most conclusive evidence exists of very recent volcanic action having been exerted on rather an extensive scale, and is also still persistent in several localities within the area named, though in a minor degree.
It would be interesting to examine the changes of level that have evidently taken place in this State within the last five years; but as more extended observations would greatly assist us in forming conclusions on this subject, I will defer that portion until a future day.