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Show 112 psychrometer daring five days. The sky was continuously clear during this period ; wind weak, and chiefly from the west- southwest. The observations of the five days ^ September 4, 5, 7,11, and 12) agreed so nearly with each other that I felt justified in taking these as the normal conditions for the season in this altitude. While I made observations in camp in the valleys, Mr. Hance observed on different occasions on the peaks near by. Usually, in meteorological reports, the relative humidity alone is calculated, the absolute being omitted, which, however, ought to be taken into consideration when comparisons of different climates are made. Both are given in the table which follows. The absolute, low as the figure appears, would in some of the observa-tons have to be expressed by half this quantity but for Regnault's correction for altitude. Place. Day. Time, S u n r i s e . . . 8 A . m - 9a. m - 10 a. m 11 a. m . . . . 12 m 1 p. m 2 p. ra 3 p. m . .. 4 p. m . . _. 5 p . m 6 p. m 7 p. m 8 p . m 9 p. m 10 p. in Sunrise... 12 in 6 p. m 9 p. m Thermometer. Dry. o 24 F. 35 48 57 61 64.5 66. 66. 68 68.2 67 65 51 41.5 38 33.5 39 58.7 51.7 45 * Wet. o 24 F. 32 42.5 43.6 45.5 46.0 46.5 46.5 48 48.5 48 47.5 44 39 37 33.5 31.1 40.4 39.7 36.5 21.960 22.016 22.024 22.030 22.032 22.028 22.018 22.008 22.000 21. 982 21.980 21.974 21. 948 21.946 21.946 21.944 19.910 19. 973 19.972 19.956 Humidity. Absolute. Relative. Valley near Jemez Peak.. Do Do Do Do Do Do Do Do Do Do Do Da Do Do Do Top of Jemez Peak Do Do Do Sept. 10 Sept. 10. Sept. 10 Sept. 10. Sept. 10. Sept. 10 Sept. 10 Sept. 10 Sept. 10. Sept. 10 Sept. 10. Sept. 10. Sept. 10. Sept. 10. Sept. 10. Sept. 10. Sept. 10 Sept 10. Sept. 10. Sept. 10. 3.6 4.3 5.9 4.4 4.2 3.6 3.5 3.5 4.0 4.2 4.2 4.4 .5.8 5.9 5.9 5.5 2.8 2.4 3.9 3.8 100 71 66 36 30 94 23 24 25 28 58 80 88 100 41 19 38 45 Glancing at the relations of temperature, we find for the air of the valley a differ" ence in one day of 44.2 between the highest and lowest range of the thermometer, the former being reached at 4 p. m., and not at 2 or 3 p. m., as is the case in lower altitudes. While in the valley the minimum was 24°, on the mountains it was 15° higher; but while in the former the thermometer at noon indicated as high as 64°. 5 F., in the latter it did not indicate more than 58.7° F. I have often observed in New Mexico that during the night the temperature of a valley sinks below that of the neighboring height. On first thought this might appear paradoxical and at variance with what we would naturally think, since we would expect that a convex surface, like a mountain, would lose more heat by radiation than one that is concave, like a valley. One might object that the air, having cooled off on the mountain- side, rolls off into the valley aud is continuously replaced by another stratum of air not yet cooled to so great an extent; but a glance at the respective conditions of absolute humidity in the mountain and valley airs does uot, apparently, confirm this view, since it increases more rapidly in the former than in the latter. " There must, then, exist currents of a somewhat different nature. Pictet has found that at night the air at a certain height above the ground is warmer than the stratum in direct contact with it. We are, however, left in the dark as to the thickness of this warmer stratum, and as to whether in a mountainous country its existence is not questionable, on account of various currents produced by the uuevenness of the country. In regard to the barometer, we find a minimum immediately before suurise and a maximum at 11 a. in. Further, a greater difference in oscillation, as should be expected in such an altitude, which is undoubtedly due to the great contrasts in temperature. In regard to tho absolute humidity, we find a considerable diminution in the mountain- air when compared with the air of the valley. While in the latter it amounted to 4.5 grams per cubic meter, in the former it was only 3.2. We find also the difference between the maximum aud minimum of humidity much greater in the latter than in the former. Further, we find for the valley- air two maxima in absolute humidity, viz, at 9 a. m. and 9 p. m., aud in apposition two minima, viz, at 2 p. m. and immediately before sunrise. The dew point wan reached every night in these mountains. The moment of the deposition of the dew can be nicely observed by the use of an India- rubber cloth spread on the ground, the slightest film thus becoming visible when no trace of |