432 New Ouil'iues of Chemical Philosophi/. 



how water and electricity ascend into the atmosphere is a me- 

 teorological (juestiou on which philosophers entertain different 

 opinions. 



The electric spark being passed through atmospheric airj 

 light and heat are produced, which shows us the nature of com- 

 bustion ; but when it is passed through water, two gases are 

 formed. The element of heat and water produce oxygen gas, 

 the element of light and water produce hydrogen gas ; water 

 being their common basis. Consequently by the attraction be- 

 tween the water upon the surface of the ground and the elec- 

 tricity in the earth, oxygen and hydrogen gases are formed, and 

 become atmospheric air. Large quantities of water and elec- 

 tricity are thus carried up into the atmosphere from the sur* 

 face of the ground in a short time. 



In this case the atmosphere becomes heayier, and the baro- 

 meter rises ; but when a decomposition of the air takes place, it 

 is resoUed into its compone;it parts, water and electricity, which 

 descend together to the earth, as mentioned above, the atmo^ 

 sphere becomes lighter and the barometer falls. 



But as the quantities of rain, which have been collected at 

 different elevations, differ so widely from one another, a few re- 

 marks upon that subject may not be unacceptable to those 

 who are engaged in the study of meteorology. 



Of the Rain Gage. 



'^ If a rain gage be placed on the groimd,"' says Dr. Thomson^ 

 " and another at some height perpendicularly above it, more 

 rain v/ill be collected into the lower than the higher ; a proof' 

 that the (juantity of rain increases as it descends, owing perhaps 

 to the drops attracting vapour during their passage through the 

 lower strata of the atmosphere, where the greatest quantity re- 

 sides*." 



The first account that I have seen of oI)servations made on 

 two rain gages, is that published in the Philosopliical Transac- 

 tions, by Dr. Heberden in 1769. 



But from wliat is stated above by Dr. Thomson, it does not 

 appear that any satisfactory explanation has yet been given of 

 this curious experiment. It does not seem, however, to de- 

 pend upon any operation of nature l)ut what is very common. 

 When the tops of the rain-gages are placed in an horizontal po- 

 sition, the higher cannot collect so much rain as the lower, when 

 the wind is high, because, it may l)e presutned, the drops of 

 rain fall more obli(|uely upon the higher than the lower. 



Suppose the vvMid were so high that the direction of the drops 

 forms an iingle of 45 degrees with the top of a rain-gage, it 



* Dr. Tlioinsou's Chemistry, vol. iv. p. 81. 



would 



