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67. 

closing the primary switch at the left. The six-point switch at the right served to connect the tubes, in order, to the high-tension side of the coil.

The flashes were observed at a distance of 2.24 miles on a fairly clear night; and it was found that a mass of 0.0089 grams of Victor flash powder was visible, and that 0.015 gram was strikingly visible; all the observations being made with the unaided eye. The minimum mass of flash powder visible at this distance is thus surprisingly small.

From these experiments it is seen that if this flash powder were explored on the surface of the moon, distant 220,000 miles, and a telescope of one foot aperture were used -- the exit pupil being not greater than the pupil of the eye (e.g., 2 millimeters) -- we should need a mass of flash powder of 

2.67 lbs., to be just visible, and
13.82 lbs., [[underlined]] or less [[/underlined]], to be strikingly visible.

If we consider the final mass of the last "secondary" rocket plus the mass of the flash powder and its container, to be four times the mass of the flash powder alone, we should have, for the [[underlined]] final mass of the rocket [[/underlined]], four times the above masses. These final masses correspond to the "one pound final mass" which has been mentioned throughout the calculations.

The"total initial masses", or the masses necessary for the start at the earth, are at once obtained from the data given in Table VII. Thus if the start is made from seas-level, and the "effective velocity of ejection is 7,000 ft/sec., we need 602 lbs. for every pound that is to be sent to "infinity".[[superscript]] (6) [[/superscript]]
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(6) A simple calculation will show that the total initial mass required to send one pound to the surface of the moon is but slightly less than that required to send the mass to "infinity."