FOREIGN CORRESPONDENCE. 427 



powdered iron, which is gummod to the leaves, that if a magnet be thrust' 

 into a package on being withdrawn it will be found to be covered with par- 

 ticles of iron — a metal not so bad as copper, certainly, and superior to 

 gypsum, Prussian blue and black lead. 



It is often necessary to suddenly augment the power of marine steam 

 •engines, for a short period. To do so, the intensity of the furnace must be 

 increased, and this is effected either by means of an energetic ventilator or 

 introducing a jet of steam from the boiler. M. Bertin, naval engineer, pre- 

 fers the second plan, as the first often occasions loss of life if the door of the 

 furnace be opened incautiously ; but he has [invented a machine, now 

 employed on board theEesolute, frigate, by which blasts of compressed air are 

 suddenly forced, by means of a centrifugal ventilator, through the bottom 

 of the furnace. The combustion is doubled under the transitory action of 

 the jet, and the motive power increased in the same proportion. There is an 

 increase, also, of 20 per cent, in the consumption of fuel. M. Cailletet, to 

 whom we are indebted for the invention of burning the gases which escape 

 from ordinary fires, has effected the samfe for the gases of the chimneys of 

 manufacturies, utilizing the heat generated by their combustion. The gases 

 at the forges of Chenecierc, which escape from the furnaces, pass under a 

 boiler .30 feet long, which they heat, then they pass into a fire-brick cham- 

 ber containing a metal box, inside of which are thin plates of metal that the 

 gases maintain at the required temperature. 



The '-writer's cramp'' is so called, doubtless, because it is neither a crump 

 nor peculiar to penmen. It is an impotence, resulting from a complete 

 absence of harmony between the muscular and the cerebral movements. A 

 person suddenly feels he cannot write, though his hands are capable of all 

 other work not requirin(> excessive precision ; often the pen falls from the 

 fingers or involuntarily lifts itself up in th6 air, w^hen the writer must await 

 its good pleasure to descend before commencing another word. The disease 

 may be considered as incurable, and the afflicted ought to consider himself 

 happy if able to wa-ite with the left hand. The "piano cramp" is due to the 

 same cause, performers being suddenly unable to continue touching the 

 keys. Often the disease in this case manifests itself in the front part of the 

 upper portion of the arm. M. Onimus attests that the affection is not un- 

 common with violinists, and the clerks ot the Morse telegraph not only 

 suffer in the same way in their fingers, but along the whole arm. A tailor, 

 when he commenced to sew, noticed his arm turning inward, and fencing- 

 masters can observe the same phenomenon with their swords, although, in 

 both cases, the arm is capable of perfectly executing every other kind of 

 work. A cobbler suffered so much from these contractions that they aftected 

 his neck and face, causing him involuntarily to make the most hideous 

 grimaces. The feet also can be attacked. Duchenne quotes the case of a 

 turner, whose foot contracted the moment he put it on the pedal of the ma- 



