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36.

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 different from those obtained in air.

There is a large difference, however, with Infallible powder, with all three nozzles. For the medium nozzle a comparison of experiments 4 to 12, inclusive, with 35 and 36 shows that the increase amounts to 22 per cent of the velocity in air.

2. The medium nozzle gives, in general, greater velocities than the short or the long nozzle with the same length of chamber, 1, and approximately the same charges of powder. In all cases, the short nozzle gives less velocity than the medium or the long nozzle, which is to be expected.

3. The results show no appreciable dependence of the velocities upon the pressure in the tank between 7.5 mm. and 0.5 mm., and it is safe to conclude that the velocities are practically the same from atmospheric pressure down to zero pressure, except as regards the slight increase of velocity with decreasing pressure already mentioned.

4. A comparison of the results when the chamber moved under the influence of the spring with those in which the chamber was merely lifted, show that the agreement of results obtained by the two methods is good provided the displacement in the direct lift experiment is small (compare experiments 40 and 41 with 26). If, on the other hand, the displacement in the direct lift experiment is [[underlined]] large [[/underlined]], this method gives considerably less velocities than the spring method. A comparison of experiments 35 and 36 with 34, 37 and 43 makes it evident that[[underlined]]  all the velocities obtained by [[/underlined]]