

METEOROLOGY. 



573 



conclusion on this subject, in the next section.) 

 All the observations thus coincide in finding in 

 the upper atmosphere much less vapor than 

 Dalton's hypothesis requires the tension and 

 quantity of vapor being reduced at a rate much 

 more rapid than can be supposed to occur in 

 an independently subsisting vapor atmosphere. 

 In reality, the tension diminished to \ by an 

 ascent of only about 8,000 ft., instead of 30,000. 

 The practice of subtracting the vapor tension 

 from the total barometric pressure, to find the 

 simple gaseous pressure, is hence absurd ; and 

 the indications of the barometer thus "cor- 

 rected " (as it is expressed) have no true mean- 

 ing whatever. 



The quantities of vapor disseminated in the 

 upper parts of the atmosphere being very small, 

 it follows that inequalities of level on the 

 earth's surface, insignificant in respect to the 

 dimensions of the globe, become of great im- 

 portance in connection with the atmosphere 

 and atmospheric phenomena. Three fourths of 

 the whole mass of air is within range of the 

 influence of the highest mountains; one half 

 the air, and nearly nine tenths of the vapor, 

 are concentrated within about 19.000 ft. of the 

 sea level, a height hardly exceeding that of the 

 mean level of the crest of the Himalayas ; 

 while one fourth of the air and one half of the 

 vapor are within a height of 8,000 ft. Mount- 

 ains, even of moderate magnitude, may thus 

 produce important changes in respect of move- 

 ments, temperature, and hygrometric state, in 

 considerable masses of atmosphere, and this 

 especially in those strata that contain the great 

 bulk of the watery vapor, and that have the 

 greatest effect, therefore, in determining the 

 character of the climate. 



Meteorological Observations in Balloon As- 

 ns. An account of the balloon ascen- 

 sions of Mr. Glaisher for scientific purposes will 

 be found under the title "Ballooning." As 

 might be anticipated in first attempts, the scien- 

 tific observations made appear not to have been 

 of very great extent ; but some of them are, 

 nevertheless, valuable. From the observations 

 on temperature, which were among the most 

 complete, the following table, including four 

 of the ascents, was constructed. In it are 

 shown the actual temperatures at the earth 

 and for every 5,000 ft. of elevation, and also 

 the corresponding decrease of temperature be- 

 tween any two consecutive elevations : 



The results of July 17 are highly anomalous. 

 Up to 10,000 ft. the decrease accords with that 

 of the other experiments ; from 10,000 to 20,000 

 ft. a remarkable deviation occurs ; while above 

 25,000 ft. the results again accord. Proceed- 

 ing upon the data obtained up to 10,000 ft., and 

 again at 25,000 ft., it results that at 15,000 ft. 

 there was an excess of 8. 3 of temperature; 

 at 19,500 ft., 22. 2 excess; at 20,000 ft. 13. 5 

 excess. The average decrease of temperature 

 is seen to be over 20 for the first 5,000 ft., and 

 over 10 for the next; while for 25,000 ft. it 

 is nearly 51. In another table, including the 

 eight ascents, and giving the temperature for 

 each 1,000 ft., from the earth up to 5,000 ft., 

 the mean decrease of temperature is found to 

 be more than 21 for the first 5,000 ft., so that 

 full of the whole decrease of temperature 

 within 5 miles of the earth takes place in the 

 first mile. The decrement of temperature in 

 the several series of observations is not uni- 

 form, either for the whole height reached or for 

 the first mile. Further elucidation on this 

 point is desirable, particularly in reference to 

 the influence of the irregularly decreasing tem- 

 peratures of the strata of air on atmospheric 

 refraction. 



The observations made in respect to the hu- 

 midity of the atmosphere show that the pro- 

 portion of vapor decreases continually with in- 

 crease of elevation, and in a rapidly augment- 

 ing ratio, until, at heights of 5 miles and up- 

 ward, the quantity of aqueous vapor present in 

 the air is extremely small. The electricity of the 

 ah- was found to be positive, and decreasing in in- 

 tensity with increase of elevation. A better test 

 paper being in the latter ascents employed, the 

 presence of considerable quantities of ozone in 

 the air was indicated. Mr. Glaisher concludes, 

 from his use of the aneroid barometer, that 

 such an instrument can be constructed, which 

 shall read correctly to the first, and probably 

 to the second, place of decimals, and that also 

 down to a pressure as low as 5 inches of mer- 

 cury. 



Dew Sow on the surface of Mud. The small 

 rainbows, or parts of such, seen upon spray 

 formed in various ways, are familiarly known, 

 as also the somewhat similar bows which 

 may be seen upon grass heavily laden with dew, 

 and which are known as dew bows. Professor 

 Rankine. along with other persons, witnessed, 

 on the 13th of February, 1862, a prismatically 

 colored bow, exactly resembling the dew bow, 

 but in this case displayed on the muddy surface 

 of a by road near Glasgow, and also for more 

 than a mile along the less trodden parts of an 

 adjoining turnpike road. The morning had 

 been hazy, but the mist had cleared away, and 

 the sun was shining brightly : time (Greenwich) 

 of the observation of the bows, between 12 30 

 and 1 p. M. The angular dimensions of this 

 iris were obviously the same with those of a 

 rainbow of the first order; its colors were 

 complete, from red to violet, and very bright 

 and distinct, especially where the mud was 



