354' MESSRS. R. H. FOWLER, E. G. GALLOP, C. N. H. LOCK AND H. W. RICHMOND: 
Column 7 gives two entries. The first is the value of QT for each round, where T 
is the mean value of the observed period and 0 corresponds to the observed value of 
the steady rate of increase of <j> from column 4. 
The second entry in column 7 is the velocity of the shell at the middle point of the 
range of periods whose mean value T is used to determine QT. The stability factor 
deteiauined by QT is taken to correspond to this velocity Finally, in column 8, the 
values of &(£) are given with their proper sign as determined incidentally in the 
determination of their times of occurrence (§4.11). 
The effect of the cards on the observed value of the period and on s, is ignored in 
Tables V. and VI. The results obtained here are corrected for this effect, as far as 
possible, before use in Table I. The information given in Table VI. is deduced 
directly from Table V. by the equations of §4.11. In certain cases where the yaw 
was large it was checked by use of the chart of § 3.7. 
The total percentage spread of the values of s (or /ul) in the group is-in most cases 
satisfactorily small. The value of 6 • 7 per cent, for the high velocity group of type I. 
shells is probably partly due to the fact that the fuzes of shells 1 to 4 were slightly 
damaged before firing in forcing the shells into the cartridge cases. 
At a velocity of 1580 f.s. results were obtained with guns of both twists of rifling. 
The couple deduced from the results for the gun rifled one turn in 40 calibres is, in the 
cases of shells of types I. and III., slightly smaller than that deduced from the other 
gun. This is to be expected as the stability in this case is nearly critical and the 
maxima are rather large (one maximum is as much as 13 degrees for a type I. shell). 
The solution of § 3.6 can hardly be expected to apply. The next term in the expression 
for /n of the form /x, sin 3 S may be expected to be becoming appreciable here ; apparently 
its sign is such that it will tend to diminish the observed value of /x, in agreement 
with wind channel observations (fig. 2). For the shells of type II. the maxima of 
the yaw are small in both guns and the results are in agreement. 
No perceptible dependence of s on the maximum yaw among the rounds of any 
one group has been detected in these tables. 
The agreement between the results for the two guns at this velocity, and between 
rounds with different maxima of the yaw, is therefore a satisfactory confirmation of 
the theory. 
The values of h + K and Ji — k + 2y, deduced from the observations as explained in 
§4.12, are given in Table VII. Of these, the former is more reliable as it does not 
depend on /8 X (t) which is difficult to determine. The actual values vary considerably 
from round to round, and only mean values for each group are shown. The results 
are therefore very rough, but they indicate qualitatively the nature of the damping, 
which may also be studied in figs. 12 and 14. For example, in fig. 14c, the motion 
starts with /3 1 ( t) positive, so that the loop encloses the origin, O, or point of zero yaw. 
But since Ji — k + 2y>0, /3 X (t) diminishes and has become negative by the second 
minimum, the loop failing to reach 0. As /3 X (t) diminishes further, the loop shrinks to a 
