NO. 2 METHOD OF REACHING EXTREME ALTITUDES 3 1 



The length of chamber, 1, in the third column, is taken as the 

 distance shown in figure 2 (a). 



In the cases of simple harmonic motion in which do is not given 

 in the table, the displacements were so large that d, was prevented 

 . from reaching its full extent by the yoke, Y, plate 7, figure i. 

 Correction for friction was made in these cases by choosing the decre- 

 ment from some other experiment that would be likely to apply. The 

 number of this experiment is written in parenthesis, in the table, in 

 place of do. The same procedure is followed in the experiments with 

 direct Hft. 



Of the experiments in the cylindrical tank, 15 and 16 were per- 

 formed with the elbow E, figure 17, at the lower end of the 3-inch 

 pipe; no. 17 was performed with this elbow also in place, with the 

 addition of a sheet-iron sleeve in the pipe, to decrease the curvature 

 at the elbow; nos. 18 and 19 were performed with the tank empty; 

 and the remaining experiments were performed with the fencing, 

 already described, "in position. 



The tissue paper was usually torn at one end, and not torn com- 

 pletely off. It was only torn completely off, with small charges, in the 

 experiments with the cylindrical tank empty (nos. 18 and 19). The 

 tissue paper was cut o'ne-third across at each end, as already ex- 

 plained, in experiments 15 and 7,3, inclusive. 



The direct-lift impulse-meter was used in experiments 15 to 26, 

 inclusive. In cases in which there was impact of the chamber agauist 

 the yoke, or pins, at the lower ends of the rods, R, R, plate 6, 

 figure 2, this impulse-meter was useless because of the jar. Only in 

 experiments 16 and 22 was there a measurable displacement, the 

 negligible displacements in the other cases being doubtless due to 

 friction. The spring impulse-meter was used only in the last six 

 vacuum experiments. 



An inspection of tables II and III will show that the results, under 

 the same conditions, are in sufficientl}^ close agreement to warrant 

 the comparison of results obtained under various circumstances of 

 firing. 



DISCUSSION OF RESULTS 



I. There is a general tendency for the velocities in vacuo to be 

 larger than those in air, for the same length of chamber, 1, and the 

 same mass of powder. 



With Du Pont powder, the medium and short nozzles give greater 

 , velocities in vacuo. The long nozzle, however, does not show results 

 very much dififerent from those obtained in air. 



