416 



Capt. Noble. Note on the Energy absorbed [Feb. 4, 



variations in the energy developed in the gun. Variations in energy, 

 under precisely similar conditions, might easily amount to 1 or 2 

 per cent., or occasionally more, and, as will be subsequently seen, the 

 differences between the uniform and parabolic rifling, although always 

 in the same direction, are not the same in all the series, and the mean 

 of the whole will probably give the most reliable result. 



Summing up the results at which we have so far arrived in the 

 experiments I have discussed, it appears that the total loss of energy 

 Arising from the fouling of pebble powder and from the friction due 

 to the parabolic rifling together amounted to close upon 7 per cent, of 

 the whole energy developed. 



The third and subsequent series of experiments were made some 

 weeks later, and from climatic or other causes there was a slight 

 but decided decrement in the energy obtained with the amide powder. 

 This decrement did not in any way affect the experiments except that 

 the absolute values of the energies at the different dates are not 

 strictly comparable. 



The object of the third series was to ascertain if a narrow driving 

 band would rotate the projectile equally well, as with an increasing 

 twist it is important, if rotation be secured, that the breadth of the 

 driving band be as small as is convenient, and further, as in the last 

 series, to ascertain the loss of energy due to the uniform and para- 

 bolic rifling. 



The results of this third series were as shown in the following 

 table: 



Table IV. Results of Experiments with Rings of Section " B." 



