124 Capt. Noble. Preliminary Note on the [June 1(5, 



this extra energy must be obtained from the development of higher 

 pressures in the forward portions of the guns, and it naturally became 

 a question of considerable importance to determine over what surface 

 these higher pressures extended, and to ascertain if they in any 

 serious degree affected the safety of the chase. 



At Woolwich, to settle this point, certain guns were prepared in 

 which crusher gauges were placed at various points along the bore, 

 and results were obtained to which I shall presently more particularly 

 allude ; but, considerable doubt having been thrown on the reliability of 

 these crusher gauges, I considered it desirable in a matter of so great 

 importance to ascertain the pressures by altogether independent means, 

 and thus either confirm the crusher-gauge results, or, if the two sets 

 of results should prove to be not altogether in accordance, to throw 

 some light upon the causes of such discrepancies as might exist. 



The crusher gauge is, to those who interest themselves with such 

 subjects, so well known, that I shall not attempt here to describe it, 

 and I will only say that I have very great confidence in the accuracy 

 of its results when properly used. Personally I have during the last 

 twenty-five years made many thousand observations with these 

 gauges, and when properly prepared and judiciously used, not only 

 have I found their results accordant inter se, but I have by totally 

 different determinations corroborated their accuracy. But I have always 

 held that this gauge and all similar gauges will cease to be either 

 reliable or accurate if there be any probability of the products of ex- 

 plosion being projected into the gauge at a high velocity, the energy 

 stored up in such products being impressed on the gauge in the form 

 of pressure, and this contingency might and does arise either when 

 the gauge is placed in the forward part of a gun, where necessarily 

 the products are in rapid motion, or in the case of the detonation of 

 a high explosive ; but, as I have gone pretty fully into this question 

 elsewhere, I need not here pursue the subject further. 



The crusher-gauge determinations for cordite, made at Woolwich 

 for the Explosives Committee, under the presidency of Sir F. Abel, 

 having been made in a 4' 7-inch quick-firing gun, I arranged a similar 

 gun in such a manner that I was able to obtain a curve determined 

 from the time at which the projectile passed sixteen points arranged 

 along the bore. From this curve, by methods I have elsewhere 

 described, the curve giving the velocity at all points of the bore can 

 be deduced, and from the curve of velocity the pressures generating 

 these velocities can also be deduced. 



For the particular purpose of this investigation it was desirable to 

 compare the pressures of different explosives, and the present note 

 gives the result of four explosives differing widely in nature and in 

 composition. 



The explosives used were as follows : 



