176 



THE POPULAR SCIENCE MONTHLY. 



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hollow cylinder, perhaps an inch long. He then slips the ring 

 back over the stick as in A (Fig. 8), or he may trim the stick 

 and cylinder as in B or C, previous to readjusting them, to form 

 the shape almost universally in use. 



Among the latest devices in the way of whistles are the cu- 

 rious chemical toys made with picrate of potash. When the 

 whistling rockets and fire-pieces first appeared, the whistling 

 was commonly supposed to be produced in the same way as in 

 ordinary whistles, by the air-movements produced by their rapid 

 motion. This is, however, not so. The operation is not at all 

 like that of an air-whistle, but the j^roduction of the sound is 

 owing to the peculiar property of picrate of potash of whis- 

 tling when it is burned. This effect is heard very clearly with 

 that salt when compressed in a tube, and the sonority may be 

 augmented by the addition of various substances. Such a 

 composition may be formed, with no other danger than usually 

 attends the manipulation of explosives, by triturating a mixt- 

 ure of fifteen parts of picrate of potash and one part of Ju- 



dsean bitumen. It is then charged into a 

 pasteboard tube a little less than a half -inch 

 in its interior diameter, and some two and 

 a half inches long (Fig. 9). The tube is 

 closed at one end by a plug of closely 

 tamped clay. The composition is intro- 

 duced in small charges evenly compressed, 

 till the tube is filled to within about three 

 quarters of an inch of the open end. The 

 whistle may be wired upon the cartridge of 

 a rocket, when it should be furnished with 

 a cap penetrated by a quick match, which, 

 entering the picrated composition, is also 

 inserted into the throat of the rocket, so 

 that the two fire-works shall be inflamed at 

 the same time. The sound of these whistles 

 is sharp at first, and passes gradually, as 

 the tube is emptied of its contents, to a grave tone. By combin- 

 ing the whistles with various devices of fire-works, curious effects 

 are produced, in accordance with which expressive descriptive 

 names have been given to the artifices. 



When the picrate whistles were first exhibited at Havre, on 

 the occasion of the Fete nationale, the spectators, irritated at the 

 strident noise they made, and mistaking its origin, exclaimed : 

 " Down with the whistling fellows ! duck them ! " The enjoy- 

 ment of the festival was much enhanced when the joke was ex- 

 plained. — Translated for the Popular Scie7ice Monthly from La 

 Nature. 



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Fig. 9— Picrate of Potash 

 Whistle, a, the whistling 

 composition ; b, rocket 

 with whistle attached. 



