C. E. Munroe — Effects of Detonation of Gun-cotton. 49 



the breakers or lines of waves appear to be divided pretty 

 sharply into two groups of different amplitudes, the exterior 

 group having the greatest amplitude. In all cases the crests of 

 the waves are turned from the center, so that if the hand is 

 passed from the center outward over the plate it glides freely, 

 but if passed in the opposite direction it is caught by the sharp 

 projecting points. This feature can easily be seen with a 

 pocket lens. 



The impression produced is shown in section in fig. 3 where 

 AE represents the extreme area having a diameter slightly 

 greater than that of the can. B the position of the wet gun- 

 cotton disk before detonation. B'B f the impression produced 

 by the base of the disks. B ' C the space where the waves are 

 not visible to the naked eye. CD and DA the spaces occu- 

 pied by the two groups of breakers visible to the naked eye. 

 B E represents the eroded and fused metal which marks the 

 most deeply indented part of the plate. The cross-section of 

 the beam F shows very clearly that the area of marked depres- 

 sion extends much beyond the limit of area of the gun-cotton, 

 and quite to, if not beyond, the extreme area of the base of the 

 can. • The experiment, as described above, has been repeated 

 several times and always with the same result. 



Dr. John Trowbridge has very kindly measured for me the 

 intervals between the breakers in the outer group, these meas- 

 urements being taken from crest to crest at six different points. 

 As, owing to the nature of the object, nothing remained sharply 

 in focus under the microscope of the comparator, the results 

 are only approximate. The data are as follows, the lengths 

 being given in millimeters : 



No. 



R. 



D. 



R. 



D. 



R. 



D. 



R. 



D. 



R. 



D. 



R. 



D. 



1 



2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 







3-6 

 5-1 

 7-7 

 9- 



11- 



12-5 



* 



3-6 



2-1 



2- 



1-3 



2" 



1-5 







3> 



4-7 

 6-5 

 8- 

 9-5 

 11-5 



3- 



1-7 



1-8 



1-5 



1-5 



2- 







3-1 



4-8 

 6-6 

 8-3 



10- 



11-3 



3-1 

 1-7 

 1.8 

 1-7 

 1-7 

 1-3 







3- 

 4-3 

 5-7 

 7-5 

 9-1 

 10-8 



3- 



1-3 



1-4 



1-8 

 1-6 

 1-7 







2-6 



4- 

 5-5 

 7- 

 8-8 

 10-3 



2-6 

 1-4 

 1-5 



1-5 

 1-8 

 1-5 







2-8 



3-9 



5-7 



7* 



8'5 



10- 



11-9 



12-5 



2-8 

 1-1 

 1-8 

 1-3 

 1-5 

 1-5 

 1-9 

 6- 



These measurements were taken from the exterior toward 

 the center of explosion, and it will be noticed that the first 

 interval is about twice as great as any of the others in a set. 

 Examination of the photo-engraving shows that at this point 

 the propagation of the undulations must have .been affected by 

 the retaining walls of the containing vessel. Omitting this inter- 



Am. Jour. Sci. — Third Series, Vol. XXXYI, No. 211. — July, 188S. 

 4 



