196 TENTH ANNUAL REPORT OF 



and ITth. The rain on the 12tli was accompanied by lightning and 

 distant thunder, but that on the 17th was the heaviest, measuring 

 0.20 inch. Although June is regarded as one of the dry months, 

 still we find, in a journal of one of our pioneers, that "it poured 

 during the night of the 11th June, 1849," and, as is seen in the tables, 

 it has rained a little in this month every year. The wind was high 

 about the period of the solstice, but the barometer did not fall below 

 thirty inches at that date. 



July was remarkable as being the hottest month yet observed.^ At 

 3 p. m. of the 13th, for the first time since we have been keeping a 

 meteorological register, the several thermometers distributed in va- 

 rious parts of the lower story of our brick residence marked 100° and 

 upwards, and remained at that height until 5 p. ra. One placed near 

 the door of the southern front, and somewhat exposed to the eifect of 

 reflected insolation, although ten feet from the sunshine, rose to 10t°. 

 In several wooden buildings through which the solar heat penetrated 

 and accumulated, the mercury was seen by us as high as 110° ; but 

 this is not so high as apparent when we take into consideration the 

 fact that the atmosphere here is always filled in the summer season 

 with particles of dust and sand, which form, as Humboldt says, " cen- 

 tres of radiant heat." All these observations were made, although 

 to the windward, still near the locality of the great fire which occurred 

 about 3 p. m. on the 13th. Now, as the 12th, 13th, and 14th were 

 the three hottest days, and the mercury did not rise higher than 98° 

 on the first, and 99° on the last of these days, it is not unphi- 

 losophical to attribute the solitary instance of extreme heat to the 

 dryness of the atmosphere, artificially increased by the conflagration, 

 and which measured 42° by the thermometer of Daniells' hygrometer. 

 And such an inference is sustained by the fact that on the 13th the 

 wind was from the southwest, which is much cooler and moister than 

 that of northwest, which prevailed on the 12th and 14th. The mean 

 temperature of the hottest part of the day for the week ending July 

 15th, was 97°. During the last half of the month the weather mod- 

 erated considerably, showing a difference of about 8° between the 

 mean maximum temperature of the first and last half, 



August was characterized by the usual atmospheric changes which 

 usher in the autumnal season. The night of the 16th was the hottest 

 night as yet noticed in the country, the thermometer standing at 82° at 

 10 p. m., and 70° at sunrise. On the 17th the barometer commenced 

 falling, and continued to do so until it reached the minimum of the 

 month. This variation of the usual atmospheric pressure was attended 

 with fresh breezes from southeast, and followed by a slight shower of 

 rain on the morning of the 21st. After this the weather became sud- 

 denly cool, the nights being quite chilly, with the thermometer rang- 

 ing from 54° to 60°. During this month the Sacramento river fell 

 to the lowest point ever known since the settlement of the country. 



In September little worthy of remark is recorded. On the 14th, at 

 10 p. m., frequent flashes of lightning were observed in the northeast. 

 The equinox passed away without any other atmospheric disturbance 

 than a slight sprinkle of rain at daylight ; wind southwest^ fresh ; 

 barometer 30.08 inches, and thermometer at 58°. 



