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70.

far obtained in any way except in electrical discharge work. 

5. Experiments were repeated with the same chambers [[underlined]] in vacuo [[/underlined]], which demonstrated that the high velocity of the ejected gases was a real velocity and not merely an effect of reaction against the air. In fact, experiments performed at pressures such as probably exist at an altitude of 30 miles gave velocities even higher than those obtained in air at atmospheric pressure, the increase in velocity probably being due to a difference in ignition. Results of the experiments indicate also that this velocity could be exceeded, with a modified form of apparatus. 

6. Experiments with a large chamber demonstrated that not only are large chambers operative, but that the velocities and efficiencies are higher than for small chambers. 

7. A calculation based upon the theory, involving data that is in part that obtained by experiments, and in part what is considered as realizable in practice, indicates that the initial mass required to raise recording instruments of the order of one pound, even to the extreme upper atmosphere, is moderate. The initial mass necessary is likely not excessive, even if the effective velocity is reduced by half. Calculations show, however, that any apparatus in which ordinary rockets are used would be impracticable owing to the very large initial masses that would be required. 

8. The recovery of the apparatus, on its return, need not be a difficult matter, from the fact that the time of ascent even to great altitudes in the atmosphere will be comparatively short, due to the high speed of the rocket throughout the greater part of its course. The time of descent will also be short;