Popular Science Monf/ili/ 



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jectile; second, its prolonged exposure 

 while in the air to the deviating sweep of 

 the wind; third, the fact that a slight roll 

 of the gun platform will greatly change the 

 arc of travel and, therefore, the range of 

 the shell; and, finally, that the target 

 offered by either the periscope or the 

 conning tower of a submarine under way 

 is a mark that is very hard to "range" 

 accurately. 

 These points 

 are mention- 

 ed in order 

 to emphasize 

 the advan- 

 tages of the 

 Isham type 

 of diving or 

 torpedo shell 

 which can be 

 fired over a 

 flat t r a- 

 jectory like 

 any ordinary 

 projectile 

 from a naval 

 gun. 



The Isham 

 torpedo shell 

 was original- 

 ly intended 

 to attack the 

 under -water 

 body of an 

 armored ship and thus to reach her vitals. 

 In the invention's present form we see a 

 shell especially and peculiarly suited for 

 battling with U-boats at long range even 

 though the enemy craft offer but the 

 smallest possible mark — the exposed tip 

 of a periscope.* Three years ago the 

 Isham shell was tested by a board of 

 naval officers, and v/hile the fuse did not 

 function satisfactorily in its entirety it 

 showed even then that the designer 

 was working in the right direction. The 

 projectile, however, demonstrated that 

 its author, by employing an unusual type 

 of nose, could make the shell dive, on 

 striking the water, and thereafter pursue 

 a submerged course at a gradually in- 

 creasing depth below the surface. 



It Dives and then Explodes 



The trial board reported that "a high 

 explosive shell is an urgent necessity for 

 naval use in addition to the armor- pierc- 



The missiles fall all about the U-boat and form a veritable 

 subaqueous barrage — an under- water curtain of fire 



ing shell now adopted." And the same 

 commission stated: 



"It would he liit,'li!y (iesiriil)Ic to have a high- 

 explosive shell liaviiif,' a fuse sueli as has been sug- 

 fiesteil hy Mr. Isham, viz, to detonate a shell on 

 strikiiifi thin metal, such as the side of a destroyer, 

 but which in striking' water would not detonate until 

 alter a period of approximately a second — this in 

 order that a shell which struck short of a sliii) might 

 continue its run under water and explode on con- 

 tact with the 

 under - water 

 body or near it." 



Since that 

 time, Mr. 

 Isham has 

 developed 

 a fuse that 

 he declares 

 will do all 

 of the fore- 

 going things 

 and more, 

 i.e., it will 

 explode after 

 a certain 

 time, follow- 

 ing a dive, 

 even should 

 it fail to 

 meet an ob- 

 stacle in its 

 path, and if 

 it hit a solid 

 body, wheth- 

 it will burst within 

 a second thereafter. 



er thick or thin, 

 one hundredth of 



When, the projectile impacts with water 

 the momentary checking of its speed fires 

 a time element or "train" of powder which 

 must be consumed before the flame 

 reaches the primer which actually de- 

 tonatesthe high-explosive bursting charge. 

 If it hits either thin or thick plating, a per- 

 cussion cap instantly sets off the prin- 

 cipal mass of high explosive. Hydrostatic 

 pressure does not interfere with the 

 functioning of the fuse. The moment a 

 submarine is seen from afar, the gun will 

 be loaded with the Isham projectiles and 

 hurled at the foe, the missiles forming a 

 veritable subaqueous barrage and creating 

 an under-water curtain fire one or two 

 hundred feet short of the target, so that 

 the shells may strike the body of the 

 submarine and explode or, failing in this, 

 be detonated like so many mines near 

 by and wreck the undersea craft. 



