394 Miscellaneous Intelligence. 



extensive marshes: 20,000 men were at work upon it day and 

 night, and it is said that 7000 died of fatigue. The sides of the 

 canal were soon covered with palm-trees, for the cultivation of 

 which the Chinese pursue a particular method. — Allg. HandL 

 Zeitung, 1825. 



4. Method of removing fixed Glass Stoppers. — M. Clausen recom- 

 mends that in these cases a piece of woollen list should be passed 

 once round the neck of the bottle, and the two ends taken by two 

 different persons ; then the bottle being held firm, if the persons 

 draw the list alternately towards them, the friction upon the neck 

 of the bottle will soon warm it so much as to enlarge the glass, 

 and allow the ready removal of the stopper. In place of this M. 

 Chevalier recommends the old process of warming the neck either 

 by a hot coal or a flame. He adds, if the top of the stopper is 

 broken off so that no hold of it can be taken, the bottle should, 

 after being warmed, be enveloped in a cloth, so as to leave the 

 neck free, and then be struck upon the bottom (by the hand). 

 Generally the first blow will make the stopper fly out ; but some- 

 times several successive blows are required to effect the separation. 



5. On the Causes of Diffraction, by M. Haldat. — The phenomena 

 of diffraction, the examination of which, in latter times, has fur- 

 nished such powerful arguments against the hypotheses of Newton, 

 and drawn philosophers towards the opinion of Descartes, have 

 appeared to M. Haldat as if they had hardly been sufficiently dis- 

 cussed in relation to the circumstances which might modify or 

 elucidate their cause. It is with this in view that he has under- 

 taken numerous experiments, in which the bodies producing diffrac- 

 tion, which he calls diffringent bodies, have been submitted to the 

 action of agents the most proper to modify them, and as an attrac- 

 tive force is the power by which the Newtonians explain diffraction, 

 he used in his trials all those agents most likely to affect it. 



After assuring himself, as had been announced by other experi- 

 menters, that this phenomenon was not modified either by the 

 specific gravity or the chemical nature of the body, M. Haldat 

 turned his attention to the strongest natural powers ; heat, elec- 

 tricity, magnetism, electro-chemical currents, and finally, affinity, so 

 powerful in modifying the attractive force, have been successively 

 and simultaneously employed to modify the state of the body, whilst 

 it exerted that influence upon the luminous rays which occasions 

 diffraction, without, however, producing any sensible alteration in 

 the phenomena. Thus metallic wires and diffringent plates of iron, 

 copper, and silver, have been heated to whiteness, and cooled to 

 14° F. ; and yet the coloured bands produced by their action upon 

 the rays of light have not presented an appreciable difference from 

 those produced by the same bodies at common temperatures. 



Diffringent wires and plates have been made the channels for 



