. The literary digest. sually travels at a speed greaterthan the velocity of sound, there is also to be heard the report ofthe exploding powder which travels forward with the ordinaryvelocity of sound. Hence two explosions will be heard, each dis-tinct in time. The circumstance that this fact was long miscon-strued by practical observers, but when actually noticed frequentlyreceived grotesque explanations, and that ultimately my as the correct one. appears to me in itself a sufficientjustification that researches such as we are here speaking of arenot utterly superfluous even
. The literary digest. sually travels at a speed greaterthan the velocity of sound, there is also to be heard the report ofthe exploding powder which travels forward with the ordinaryvelocity of sound. Hence two explosions will be heard, each dis-tinct in time. The circumstance that this fact was long miscon-strued by practical observers, but when actually noticed frequentlyreceived grotesque explanations, and that ultimately my as the correct one. appears to me in itself a sufficientjustification that researches such as we are here speaking of arenot utterly superfluous even in practical directions. That theflashes and sounds of discharging artillery are used for estimatingthe distances of batteries is well known, and it stands to reasonthat any unclear theoretical conception of the facts here involvedwill seriously affect the correctness of practical calculations. It may appear astonishing to a person hearing it for the firsttime that a single shot has a double report due to two different. Fig. I.—Photograph of a Blunted Projectile. velocities of propagation. But the reflection that projectileswhose velocity is less than the velocity of sound produce no head-waves (because every impulse imparted to the air travels forward,that is, ahead, with exactly the velocity of sound), throws fulllight when logically developed upon the peculiar circumstanceabove mentioned. If the projectile moves faster than sound, theair ahead of it can not recede from it quickly enough. The air iscondensed and warmed, and thereupon, as all know, the velocity of sound is augment-ed until the head-wavetravels forward asrapidly as the projec-tile itself, so that thereis no need whatever ofany additional aug-mentation of the velo-city of such a wave wereleft entirely to itself,it would increase inlength and soon passinto an ordinarysound-wave, travelingwith less velocity. Butthe projectile is alwaysbehind it and so main-tains it at its properdensity and velocit
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1890
