454 RECENT PROGRESS IN PHYSICS 



far and wide. All the following experiments were made under a bell 

 glass, and the scattered pieces collected on a sheet of paper at the 

 bottom. 



A j^latinum wire, 0.0258 lines radius, 19 lines long, becomes red hot 

 with s r= 5 and q-=.l\\ with g = 20 it broke and melted. Many pieces 

 \ line long had globules at their ends ; a few splinters were melted 

 together. A similar platinum wire melted into a number of small 

 perfectly round globules with q-=: 22. 



A silver wire, 0.0264 semi-diameter, 20 lines long, broke and melted 

 with 8 =r 6, g = 26 ; some globules and fragments fused together were 

 collected. 



A tin loire, radius 0.037, length 15, with s =z 5, g = 20 ; globules 

 dropped which oxidized in dancing about with the well known scin- 

 tillations. 



A copper loire, radius 0.0253, length 16 lines, with s =: 6, (? = 20 

 ignited ; with q = 25, was converted into very small globules. 

 Larger globules could not be obtained from copper. 



The charge producing perfect fusion here, is not much greater than 

 that which produced the first red heat. Hence, with the oxidizable 

 metals, the temperature is elevated by receiving oxygen from the air, 

 chemical effects uniting with the electrical. This is most remarkable 

 in iron, which often melts with charges, that directly would have 

 produced only a moderate ignition. 



An iron loire, radius 0.0266 length 17 lines^, came to a bright red 

 heat with s = 3, g = 13 ; but this did not cease in an instant, as in 

 the other cases. The ignition increased to a white heat ; then some 

 globules dropping from the wire rolled about on the paper^ giving off 

 an abundance of sparks. 



The residue of the charge remaining in the jar after the fusion of a 

 wire, is very considerable ; in one of Riess' experiments it amounted 

 to nearly 23 per cent, of the whole charge. 



4. Dispersion. — The first directly visible effect of the electrical 

 discharge on a new wire, consists, as before remarked, in the forma- 

 tion of a cloud of vapor rising from the surface. It is probable that 

 this consists of particles of metal separated from the exterior of the 

 wire, the quantity depending upon the condition of the surface. By 

 increasing the charge beyond the point at which it would perfectly 

 fuse the wire, it is possible to convert the whole mass of the wire into 

 such a vapor. This takes place with a brilliant development of light, 

 and a loud report. 



A platinum wire, (radius 0.0309 lines, length 15 lines,) ignited 

 with s rr: 5 and g- r= 13, and with 5' m 17, melted into globules. A 

 similar platinum wire was dissipated with brilliant light, with q = 

 22, and in tlie tube surrounding it appeared a gray deposit. 



The same experiment was repeated in the open air, and a few lines 

 above the wire a plate of mica was held ; it was covered by the dissi- 

 pation of the wire with gray and blackish flakes, which, under a mi- 

 croscope of 280 magnifying power, seemed to be composed of particles 

 of metal of different sizes and form. 



The more brittle the metals are, the more easily are they dispersed. 



