ALEXANDER MACFARLANE-RAINMAKING. 79 
balloons, which carry the conduits into the proper strata of air. By the 
action of the fans the cold air is drawn down one conduit and forced up 
and out of the top of the second conduit directly into the humid current 
of air, thus causing one upward and one downward current of air.” 
This plan supposes that a tube such as described can be held in the air 
by balloons held captive by ropes, the one at a height of perhaps 2000 
feet, the other at a height of 1000 feet. This is rather a difficult postu¬ 
late to realize. But suppose that it is practicable, it is safe to say that 
the amount of rain precipitated even under favorable conditions would 
not suffice to run the steam engine. 
“ The second plan is to use a large sheet of canvas, properly strength¬ 
ened by netting. The canvas is to be supported in midair (by balloons) 
at a right angle to the course of a humid current of air; the lower cor¬ 
ners of the canvas are to be controlled by ropes, which reach the earth, 
by means of which the sheet can be drawn to act as an inclined plane. 
The currents striking against this inclined plane will be deflected from 
their paths and carried up. They will expand as they ascend, and will 
be brought directly into contact with the colder air above. This should 
cause rain, as in the case of mountain condensers. The humid air de¬ 
flected by a sheet 200 by 400 feet would be over four billion cubic feet 
an hour, if the current striking it travelled ten miles an hour. This vol¬ 
ume cooled should yield considerable moisture, in addition to which the 
cumulative effects of precipitation should yield much more.” 
Mr. Pitkin has calculated the amount of air which would be deflected 
upward per hour by his vertical sail supported by balloons; but he has 
not calculated the pressure which this frail structure would have to 
stand. With the wind blowing at ten miles an hour and striking the 
sail perpendicularly, the pressure would be equal to the weight of one 
hundred thousand tons. The atmosphere can not be controlled so easily; 
it would simply flatten out the sail. A mountain ridge can withstand 
the pressure; but who can stand the expense of building a mountain 
ridge ? 
8. John Jacob Astor. —Mr. Astor has an invention for making rain 
which he thus describes: “In the sketch I have shown an air tower 
erected upon an eminence, such as a cliff or a mountain, and I place in 
the valley a blower of large capacity, which communicates with the air 
tower by means of an air trunk of suitable size; and I drive the blower 
with any convenient power. In the present case I have represented an 
engine house which encloses the blower, and an engine for driving the 
same. In lieu of such an arrangement I may provide a tower of suffi¬ 
cient height to convey the air directly from the lower to the higher level, 
and I may arrange the blower and the driving mechanism in the base of 
the tower; or I may arrange the blower upon the eminence and extend 
