26 
DRS. J. PLUCKER AND J. W. HITTORF ON THE 
which by increased temperature were divided into smaller ones. Each band has a chan- 
neled appearance produced by fine dark lines, the darkness of which increases from the 
more to the less refracted extremity of the band, contrary to what takes place in the 
violet channeled spaces of nitrogen. 
Chloride of lead, when examined within our spectral tubes, showed no traces of 
bands ; they were replaced by bright lines. But on account of the great difficulty of 
vaporizing it, the spectrum of the second order, owing to lead, is best developed by 
the discharge of Ruhmkorff’s coil between two electrodes made from this metal and 
surrounded by an atmosphere of hydrogen. The spectrum of this gas being under these 
conditions nearly a continuous one (59), the bright lines of the lead-spectrum of the 
second order rise from a coloured ground. More than fifty lines were counted, although 
the fainter ones did not appear. 
71. When either chloride or bromide or iodide of copper is introduced into the flame 
of Bunsen’s lamp, we get spectra of bands, but these bands are not exactly the same, 
they differ from one another by additional bands*. In the oxyhydrogen flame the 
bands are better developed, but we did not succeed in resolving the shadows of the 
hands into dark lines. At the same time four lines of single refrangibility appeared. 
The number of these lines was increased and the number of bands reduced, when chlo- 
ride of copper was examined within our spectral tubes. The well-known spectrum of 
the second order was fully developed, and every trace of bands extinguished, by dis- 
charging Ruhmkorff’s coil between two copper electrodes. 
72. Finally, manganese exhibited a curious spectrum of the first order, most similar 
to that of carbon (third and fourth type (56)). The whole spectrum is equally divided 
into large fields, but these fields are shaded differently by fine transversal lines, the 
shadow increasing from the more to the less refracted extremity of each field. From 
the brighter less refracted part rise groups of bright lines, similar to the groups of 
carbon, but the lines of the groups are differently distributed. 
When Ruhmkorff’s large coil was discharged between two electrodes made from man- 
ganese (we surrounded them with an atmosphere of hydrogen), a pure spectrum of the 
second order, free from any traces whatever of the former spectrum, was obtained. 
Explanation of the Plates. 
In determining the different spectra both of the first and the second order, the 
dispersing prisms occupied invariably the same position, corresponding to the minimum 
deviation of the green hydrogen-line H/3, i. e. of Fraunhofer’s F. All spectra repre- 
sented in the Plates are referred to the three hydrogen-lines Ha, H/3, Hy, and the 
double sodium-line Na. Generally two prisms of about 60° and 45° were employed, 
* This fact has been noticed by At. A. Mitscheblich with regard to the chloride and the iodide, and attri- 
buted by him to the undecomposed salt (Toggendobff’s ‘ Annalen,’ 1862, vol. ii. p. 299). 
