162 THE AMERICAN MONTHLY [Sept 



delicate tools and measuring- instruments were made 

 specially for the construction of this watch. The prelim- 

 inary work in the making- of the timepiece was very ex- 

 pensive, and the selling- price is $1,250. 



A Flying Bullet. — ^Accompanying- is a diag-ram of a 

 photog-raphed projectil showing- the lig-ht interference pro- 

 duced by the sound waves which it created in its forward 

 rush. Prof. Mach, of Vienna, was the first to photog-raph 

 flying- bullets and has described his work in the Open 

 Court. The path of a flying- bullet resembles the course 



/^ 



of a ship in water. It has its head wave, or bow-wave, 

 and it has its "wake " of eddies. The head-wave, is a 

 sound wave, and when the velocity of a bullet is g-reater 

 than that of sound, the head sound-wave of a bullet 

 reaches the ear before the sound of explosion, and so, in 

 such cases, a discha^g-ing- cannon gives two reports. 



^Vhooping Cough Bacillus. — It has hitherto eluded the 

 g-rasp of the bacteriolog-ist, but has finally been captured 

 by Dr. Henry Koplik, of New York, whose discovery has 

 been confirmed by Dr. Ozapelewski, a German expert — 

 there being- only one other bacillus — that of influenza — 

 which is as small. The whooping coug-h bacillus can 

 only be seen under a very high power. It is usually in the 

 shape of a club. Dr. Koplik, who is connected with the 

 Good Samaritan Dispensary, has a laboratory adjoining- 



