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METEOROLOGY. 



METEOROLOGY. In this department of 

 science, the questions that have most engaged 

 the attention of explorers during the year past, 

 are those connected with the distribution of va- 

 por in the atmosphere, and its relation to the 

 air proper and to the barometer, as well as also 

 certain points relative to the production and fall 

 of rain. Some of the new views advanced ap- 

 pear likely to bring about important changes in 

 meteorological theories, as well as in their prac- 

 tical applications. An abstract of these views, 

 and of some other papers presenting features of 

 special interest, will be given. 



Comparative Temperatures of the Air and 

 Soil. M. Pouriau has during 5 consecutive 

 years made observations of the temperature of 

 the air at a few feet above the surface of the 

 ground, and that of the soil at a depth of 2 

 metres (about 6 ft. 6 in.). His results will, of 

 course, hold very nearly true for all countries 

 or sections having a like mean temperature and 

 climate with France, or that, in other words, lie 

 between the same isothermal lines, while with 

 some modifications, they may be applied also to 

 regions lying within the near isothermal belts 

 on either side. Of those results, the following 

 is a summary : 



1. The mean temperature in the air for the 

 year was 50.37 F. ; in the soil, 55.02 : differ- 

 ence in favor of the soil, 4. 65. 



2. The mean temperature of the soil in win- 

 ter and autumn is higher than that of the air; 

 in summer the former is about 3. 6 lower ; while 

 in spring the mean temperatures of the two are 

 very nearly equal. 



3. The mean of the extreme maximum tem- 

 peratures in the air was 94. 1 ; in the soil, 

 67. 55. On the other hand, the mean of the 

 extreme minimum temperatures in the air was 

 10. 15 ; while in the soil this minimum never 

 sank below 42. 8. 



4. While in the air the mean of the total dif- 

 ferences between the extreme maxima and the 

 extreme minima reached 115.95: in the soil 

 this mean was only 56.73. 



5. In 1860, the mean temperature of the air 

 sank to 4 ; in the soil the mean was never less 

 than 41.84. 



6. While in the air the maximum tempera- 

 ture usually occurred in July or August, and 

 the minimum in December or January, the time 

 of maximum temperature in the soil always 

 corresponded to the end of August ; the min- 

 imum always occurred at the end of February, 

 or on the first days of March. . 



7. The changes taking place in the tempera- 

 ture of the soil at the depth given may be thus 

 stated : While the mean temperature of the air 

 usually began to sink toward the end of July, 

 in the soil the heat continued to accumulate in 

 the superior layers under the influence of the 

 still intense solar radiation, and from these to 

 extend to the lower layers, until the end of Au- 

 gust. From this time, the upper layers begin 

 to lose by radiation upward into the air more 

 heat than they receive from the sun ; the flow 



of heat in the soil accordingly now changes its 

 direction, passing from the lower to the upper 

 layers and becoming lost in the air ; and this 

 ascending movement continues until February, 

 being more rapid as the external temperature 

 is lower, i. e., as the winter is longer and more 

 severe. Toward the middle of February or the 

 beginning of March, the upper layers of the soil 

 begin again to become heated under the influ- 

 ence of the solar rays, the direction of which 

 has become less oblique; the inferior layers 

 give less and less heat to the upper ones ; they 

 begin on the contrary to receive some, and to 

 become re-heated this process going on with 

 accumulating effect until August. 



Experimental Researches on Evaporation and 

 Absorption. Two papers by Mr. Thomas Tate 

 detailing such researches, with an account and 

 drawings of corresponding measuring instru- 

 ments, these being termed respectively " evap- 

 orameters" and " absorbometers," appear in 

 the " Philos. Magazine," 4th series, vol. xxiii, 

 1862. The object of the evaporameter is stated 

 to be that .of determining with considerable pre- 

 cision the amount of evaporation which takes 

 place from a given surface of water in different 

 states of the atmosphere. In one of its forms, 

 a large open-mouthed vessel has extending from 

 it, and in a line rising very slightly above the 

 horizontal as it recedes, a small tube, the ves- 

 sel being, filled with water to a certain height, 

 and the tube at the same time being filled 

 through a part of its length : a slight evaporation 

 of water from the vessel, occasions a very no- 

 ticeable recedence of the water in the tube, and 

 after a proper lapse of time, a displacement- 

 gauge,which also dips into the water, being de- 

 pressed until the liquid is returned to its first 

 position in the tube, this gauge shows directly, 

 by the level at which it then stands, the num- 

 ber of cubic inches of water in the mean time 

 evaporated. 



Among the results holding generally true in 

 reference to evaporation from a water surface, 

 it was found that other things being in each 

 case the same the rate of evaporation is nearly 

 proportional to the difference of the tempera- 

 tures indicated by the wet and dry-bulb ther- 

 mometers ; 2, the augmentation of evaporation 

 due to air in motion, is nearly proportional to 

 the velocity of the wind ; 3, the evaporation is 

 nearly inversely proportional to the pressure of 

 the atmosphere. In respect to spontaneous 

 evaporation- from surfaces of wet fabrics, &c., 

 exposed to the atmosphere, this being nearly 

 uniform so long as the temperature and hygro- 

 metric state of the air are constant, the follow- 

 ing results were determined: 1. The rate of 

 evaporation from damp porous substances of like 

 material, is proportional to the extent of the 

 surface presented to the air, without regard to 

 the thickness of the substances. 2. The rate 

 of evaporation from different substances mainly 

 depends upon the roughness or inequalities of 

 their surfaces, being most rapid in case of those 

 most uneven ; in fact, in this respect, the best 



