144 Progress of Invention. 



and which, though they weaken the current travelling along the 

 wire, augment the total effect by producing an extra excitement of 

 the battery, so that far more is gained in one way than is lost in the 

 other. He ascertained, however, from subsequent experiments, that 

 advantage is on the side of non-insulated wire only when the battery 

 is calculated to produce, or is arranged for, quantity — which greatly 

 limits the advantages that such an arrangement may possess. 

 Among these is the partial or total absence of an extra current. 

 Still more recent researches have led him to discover that a large 

 amount of the supposed superiority of the non-insulated wire was 

 due to an accidental superiority as to conducting power, which it 

 happened to possess over the insulated wire that was used in the 

 comparative experiments. Making, however, every allowance for 

 this circumstance, it is still certain that non-insulated wire is best 

 when a quantity-battery is employed. Not only is it cheaper, but 

 it allows a greater number of coils to be put within the same space, 

 which of itself augments the electro-magnetic effect. The use of 

 non-insulated wire for electro-magnetic purposes is not new. 



A new kind of Electrifying Machine. — The electro-magnetic 

 coil has, in a great measure, superseded the electrifying machine : 

 the latter, however, will never cease to be an object of interest ; 

 and, it is probable, will always be preferred for some purposes. The 

 expense and difficulty of managing large plates and cylinders of glass 

 have hitherto been obstacles to the use of large electrifying machines. 

 These obstacles appear now removed — glass being rendered unne- 

 cessary by the discovery of a far more convenient and effective mate- 

 rial. M. Edmond Bequerel exhibited to the Academy of Sciences on a 

 recent occasion an electrifying machine, the plate of which was 

 made of indurated red sulphur, the invention of a civil engineer. 

 It was eighty centimetres in diameter, and* afforded a spark fourteen 

 centimetres in length. No amalgamated cushions were required 

 with it, the skin of a cat being quite sufficient to produce every 

 desired effect. Sulphur undergoes extraordinary changes by suc- 

 cessive fusions ; becoming extremely hard and tenacious. After 

 the third fusion it no longer acts on metals, or possesses its cha- 

 racteristic odour. The plate used by M. Bequerel was formed by 

 fusing the sulphur three times in a cast-iron vessel, at a temperature 

 between 250° and 300° Cent., and allowing it, after each fusion, to 

 cool thoroughly. After the first and second fusions it was crushed 

 to a coarse powder ; and, after the third, it was poured into a plaster 

 mould. Plates four metres in diameter may easily be made in this 

 way ; they cost extremely little ; and, besides being more efficient, 

 are far less hygrometric than glass. 



New Method of Copying: Crystals. — To produce very beautiful 

 copies of crystals, M. Kuhlmann coats a thin plate of copper with 

 sulphate of magnesia or of zinc, thickened with gum ; then lays the 

 copper-plate against another, with the coated surface between, and 

 passes both plates between powerful rollers. The second plate may 

 be employed at once in printing, or it may be reproduced by the 

 electrotype. Instead of a copper-plate he sometimes employs glass, 

 taking impressions of the crystals in gutta-percha, and reproducing 



