8o 



THE POPULAR SCIENCE MONTHLY. 



brought in succession into the action of the spark until the lines of 

 the substance were clearly visible," If a skeptical person refuse to 

 believe the results of Cappel, who tells us that -^^ of a milligramme 

 (t5"8Fo o^ ^ grain) of nickel v^\S\.just write the signature of that metal, 

 what will he say when, glancing at Table B, appended hereto, he finds 

 the statement that g-ooTTo ^f a milligramme (xssootto ^^ ^ grain) will 

 sign its name in brilliant characters ! And yet the writer does not 

 hesitate to say that even a smaller amount of this metal will show a 

 spectrum, for in these experiments a much stronger spark was used 

 than was necessary to show a visible spectrum. When reduced to a 

 minimum, by means of a miniature Leyden jar, improvised out of a 

 test-tube, which still gave a distinct spectrum, the loss in weight, 

 after passing 3,000 sparks, was absolutely ina2^preciable on the balance. 

 The tables show another curious and unexpected result, viz., that the 

 loss in weight of the volatile metals very slightly exceeds, and in some 

 cases does not equal, the loss of the less volatile metals. Thus, in 

 three different experiments of 3,000 sparks each, copper loses but -^^ 

 milligramme, while gold loses y^- milligramme." ^ 



In one experiment the number of sparks was increased to 10,000, 

 and the loss in weight was nearly proportioned to the increased num- 

 ber. In this case the sparks were passed at the rate of about 250 per 

 minute. 



TABLES. 



The first column shows weight of metallic electrodes (in milligrammes) before passing 

 the sparks. 



The second column shows weight after passing 3,000 sparks. 



The third column shows total weight of metal volatilized (in fractions of a milli 

 gramme). 



The fourth column shows the amount of metal volatilized by each spark (in fractions 

 of a milligramme). 



The fifth column shows the amount of metal volatilized by each spark (in fractions of 

 a grain troy). 



TABLE A. 



Upper pole, gold 



Lower " " 



Upper " copper 



Lower " " 



Upper " gold and copper 

 Lower " " 



Upper " tin 



Lower " " 



Upper " silver 



Lower " " 



Averajre lead 



i^_ 



2 7 7 U(J 



Tgrrnnnr 



TS'TiiTToo 

 li?4 (/ITTT 



TTBTfrnr 

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19411 1) 0(T 



' " The Spectroscope in its Application to Mint-Assaying." Journal of the Franklin 

 Institute, October, 1874. Eeprinted in the Quarterly Journal of Science, January, 1875. 



