490 THE POPULAR SCIENCE MONTHLY, 



ditions : To cool down the cubic mile of air to the dew point wonld 

 require the abstraction of as much heat as would raise eighty- 

 eight thousand tons of water from the freezing to the boiling 

 point. To cool it eleven degrees more would require the abstrac- 

 tion of the same quantity of heat again. This would cause the 

 precipitation of twenty thousand tons of water, which, spread 

 over a square mile, would give 1"4 pound per square foot or 0'27 

 of an inch of rain. The amount of heat which the twenty thou- 

 sand tons of water vapor would give off to the particles upon 

 which it would condense would raise a hundred thousand tons of 

 water from the freezing to the boiling point, and this would also 

 have to be taken from the air in order to allow the condensation 

 to continue. According to this computation, enough heat would 

 have to be extracted from the air to raise two hundred and 

 seventy-six thousand tons of water from the freezing to the boil- 

 ing point in order to produce a rainfall of about a quarter of an 

 inch over an area of a square mile. This two hundred and sev- 

 enty-six thousand tons of water would cover the same area to a 

 depth of more than six inches. Accordingly, in order to produce 

 a rainfall of a quarter of an inch under the conditions mentioned, 

 enough heat would have to be taken from the air to heat a body 

 of water covering the whole area to a depth of ninety feet through 

 one degree Fahrenheit. 



To accomplish this purpose Mr. Dyrenforth proceeded to raise 

 the temperature of the air still higher by means of heat-produc- 

 ing explosives. 



Under these conditions eight balloons, a hundred and fifty 

 shells, and four thousand pounds of rosellite were fired off. No 

 rain appeared. One balloon exploded within a black rain cloud, 

 but failed to produce any precipitation. On the following Wednes- 

 day, with a clear sky, ten balloons, a hundred and seventy-five 

 shells, and five thousand pounds of rosellite were exploded, and 

 the sky remained clear. On the following night the remaining 

 stock of explosives were fired off, regardless of consequences, to 

 get rid of them. 



At the time of this national fiasco, another patented plan of 

 rain-making was published, and it was reported that Senator Far- 

 well liked it even better than the concussion plan. It proposes to 

 send up liquefied carbonic acid and to set it free in the portion of 

 air from which it is desired to precipitate the rain. The carbonic 

 acid in vaporizing and expanding must take heat from the sur- 

 rounding air sufficient to set its molecules vibrating in the gase- 

 ous form. Unquestionably we have here the proper kind of an 

 agent for producing rain. The only question to be considered is 

 one of finance. Prof. Macfarlane estimates that one pound of car- 

 bonic acid in taking the gaseous form at 72 F. would take up 



