During the year 1863 we have had but five earthquakes, and as in former years they have been marked by no serious event, if we except the light degree of fright induced at the time among our people. January 25th.—A severe shock was experienced at San Diego at 2h. 20m. M., which lasted five to eight seconds. There was no undulation in this case, it consisting of a series of sharp jars. It was preceded by a deep rumbling noise. February 1st.—A very smart shock at the Mission San Juan, Monterey County, at 4h. 1m. P.M. This shock was felt at Gilroys at 4h. 15m. This town is twelve miles east of the former. At both places the shock was marked by the undulatory motion. It was not observed at Monterey, which is nearly twelve miles west of the Mission. June——A smart shock at midnight at San Francisco. August 1st.—Two light shocks at San Francisco, at 10h. 48m. P.M., and at 11h. 6m. P.M., another shock. December 19th.—At 2h. 38m. P.M. a smart shock was felt throughout the city; directly afterwards another and more severe one occurred. The first was a short, sudden jar, while the second was undulatory. The accuracy of the telegraph operator at Santa Clara has enabled us to form a correct idea of the course of this shock, and to correct to some extent the popular errors relating to the direction of the seismic wave. His time was 2h. 44m. 31s., being within 29 seconds of true time, which would then be 2.45. This gives us only 6½ minutes difference in elapsed time, and gives for the direction of the wave an east course in place of north and south, as reported, which corresponds to our measured observations here. I take this opportunity of expressing the thanks of the Academy to this operator for his accuracy and kindness in furnishing us data in this and other phenomena of scientific and public interest. February and March, 1864. During the present year, 1864, we have had two smart earthquakes at the date of writing this report. February 26th.—At San Francisco a light shock at 0h. 40m. M., and another at 2h. 10m. M. These were reported to me by persons who were up in the south and west parts of the city. At 5h. 47m. a very smart shock occurred, having three distinct vibrations, which induced many to rise somewhat earlier than was usual. This earthquake was preceded by a strong _electric storm_ (so called here), between this city and Visalia; the particulars of which have not as yet all come to hand. It was followed next day by one of those severe “northers” with which the people of this State are very familiar. Barometer very low. This fact is mentioned only on account of the unseasonable period at which the gale occurred. This earthquake was felt more severe at San José and Santa Clara than at this place, and occurred at nearly the same hour.