L. MECHANICS AND ENGINEERING. 479 



while the shell might burst in the front rank of an advancing 

 column, the ball would continue its course through several 

 succeeding columns. 



CELLULOSE-DYNAMITE. 



Trauzl has succeeded in producing a nitro-glycerine pow- 

 der, possessing all the advantages of infusorial-dynamite, and 

 also that of gun-cotton in its indifference to the action of 

 water, by employing the property of certain organic sub- 

 stances, discovered by him, of absorbing nitro-glycerine, and 

 retaining it completely in water, in a condition perfectly ca- 

 pable of explosion. Instead of nitro-cellulose and gun-cotton, 

 first used for the purpose, he employs a peculiarly prepared 

 cellulose, which takes up 70 to 75 per cent, of nitro-glycerine, 

 and forms an explosive, which remains constant in composi- 

 tion under water, and after pressing out and drying acquires 

 its previous explosive force completely ; and which, when 

 mixed even with a large amount of water, can be exploded 

 with great effect by means of fulminates or cartridges, but 

 not by merely mechanical means. 6 (7, April 2, 1874, 136. 



lippmann's small electro-capillary motor. 



The following principle has been applied by Lippmann in 

 the construction of a very novel, small motor, producing one 

 hundred revolutions per minute, and which is so exceedingly 

 sensitive to the slightest electrical current that its use for 

 electromedical purposes is suggested, as well as its possible 

 adaptation to the reception of messages by ocean cables. If 

 a globule of mercury, several millimeters in diameter, covered 

 with water acidulated with sulphuric acid, and but slightly 

 colored with bichromate of potash, in a glass or porcelain 

 vessel, is touched on the side with an iron point, it at once 

 contracts, thus altering its shape, again expands until it 

 touches the needle point, then again contracts, and so on, 

 giving rise to curious reciprocating movements. This pe- 

 culiar effect is due to the alternate oxidizing and deoxidizing 

 effect of the bichromate and iron on the mercury, whereby 

 its capillary properties are modified ; and a similar phenome- 

 non is produced when the mercury is alternately connected 

 with the positive and negative poles of a galvanic cell. In 

 applying the force thus generated on a large scale, Lipp- 



