242 ANNUAL OF SCIENTIFIC DISCOVERY. 



was in the red portion of the electric arc, and the platinum in the 

 violet, he found the carbon volatilized, and collected on the plati- 

 num wires in a changed state. In this experiment this current con- 

 tinued for about a month in great activity, during which time a slight 

 deposit of darkish substance has been made, and which M. Despretz 

 compares to diamond dust. 



This deposite, M. Despretz says, seen through a magnifying glass, 

 presents nothing very distinctly ; when examined with a microscope, 

 magnifying some thirty times, it offers several interesting points. 

 M. Despretz is persuaded that he has distinguished octahedron crys- 

 tals, both on the platina wires (and especially at the extremities) and 

 upon the deposite itself; and M. Delafosse, a practised and an eminent 

 crystallographer, is also satisfied that he has seen black and white oc- 

 tahedrons on the platina wires. He removed the wires and placed in 

 their stead a piece of polished platina, a centimeter and a half in di- 

 ameter ; although this experiment was made uninterruptedly for six 

 weeks, no crystals were deposited on the surface. The half of its sur- 

 face was covered with almost circular curves of a larger radius than 

 the plate ; each of these curves was painted with the colors of thin 

 lamella, and here and there were small spots of grayish white, which 

 seemed to be the result of the momentary adherence of isolated de- 



/ 



posites. In another experiment, M. Despretz fixed a cylinder of pure 

 carbon to the positive pole of a weak Daniel's battery, and to the 

 other pole a platina wire, after which he plunged both of the poles 

 in weakly acidulated water ; the experiment lasted two months ; the 

 negative pole was found to be covered with a black coating, which 

 was examined with the microscope, without however discovering any 

 thing. To appreciate the mechanical properties of these two powders, 

 M Despretz sent them to M. Gaudin, an eminent lapidary, to try on 

 precious stones. He ascertained that the deposites on the platina 

 wires, mixed with a little oil, polished several rubies in a very short 

 time ; the black poAvder deposited on the wire in the water, required 

 a longer time to give the same polish. M. Gaudin believes the de- 

 posite to be the same matter as diamond dust : nothing but dia- 

 mond dust can polish rubies. 



A similar result has been obtained by decomposing a mixture of 

 chloride of carbon and alcohol by weak galvanic currents. 



In his communication to the Academy, M. Despretz concludes as 

 follows : " Have I obtained crystals of carbon which I can separate 

 and weigh, in which I can determine the index of refraction and the 

 angle of polarization without doubt ? No ; I have simply produced 

 by the electric arc, and by weak volatile currents, carbon crystallized 

 in black octahedrons, in colorless and translucent octahedrons in plates, 

 also colorless and translucent, which possess the hardness of the pow- 

 der of the diamond, and which disappear in combustion without any 

 sensible residue." 



It is understood that M. Despretz is persuaded that he will ere long 

 present the Academy of Sciences with a large crystal of carbon 

 (a diamond) and solve the difficult question which has so long mocked 

 all savants. 



