SCIENTIFIC SUMMARY. 
309' 
which approaches nearer than that of the South of France to the climate of 
the Tertiary periods. 
In his memoir M. Martins shows, in like manner, that most of the tender 
trees and shrubs of the South of France have their fossil ancestors in Ter- 
tiary or Quaternary strata, formed at an epoch when the climate of Europe 
was so warm that many plants inhabited countries where they could not 
now pass a single winter. He instances the occurrence of Chamcerops humilis 
in the north of Switzerland, of the Oleander in the Sarthe, of the Pome- 
granate in the neighbourhood oi Lyons, and of the Vine in Silesia. This 
note of M. Martins’ is an interesting contribution to the confirmation and 
extension of results already obtained by various palaeontologists, especially 
Heer and Ettingshausen, as to the filiation of the existing flora to that of 
Tertiary times. 
CHEMISTRY. 
The Absorption-Spectrum of Potassium Permanganate, and Volumetric- 
Analysis . — While concentrated solutions of this salt exhibit a broad absorp- 
tion band which blots out all the green and a part of the blue of the spectrum, 
the same liquid, when rendered very dilute, is recognized in the spectro- 
scope by the presence of five distinct and separate lines or bands, the first 
of which is near D, the last at F, and the middle one of all between E and 
b ; the first and last are considerably less dark than the others. These bands 
are readily distinguished, even after often-repeated dilution, and the second 
and third of them, which are the last to disappear, can be perceived almost 
as long as the liquid itself shows a reddish tint. In the performance of 
volumetric analyses of colourless solutions the point where the fine colour 
of permanganate ceases to be destroyed is readily determined ; if the liquid 
under examination, however, has a distinct colour which renders the reaction 
obscure to the eye, the exact stage when an excess of permanganate is added 
may be found by aid of the spectroscope. Briicke, who has devised this 
useful means of giving increased accuracy to several analytical processes in 
which permanganate is employed, makes use of a direct-vision spectroscope 
by Steinheil ; he explains, moreover, in his paper, how observations can be 
made with a common prism of 60°. In the case where it is desired to de- 
termine quantitatively a comparatively small amount of iron protoxide in 
the presence of iron oxide, the degree to which the solution can be diluted 
is limited, lest the error of observation become too great. An excess of 
permanganate, however, may be added to the yellow solution, which shall 
so little affect the tint of the liquid that it cannot be distinguished from a 
simple concentrated solution of the higher oxide. An observation with the 
spectroscope will then indicate the presence of the characteristic absorption 
lines of the manganese salt, and solution of a salt of iron protoxide of known 
strength can then be added till they disappear; and thus the necessary 
correction can be made. It is pointed out by the author that this method, 
which can be employed with complete success by such persons as are colour- 
blind, may be made use of in the case of solutions of any degree of con- 
centration or dilution. There is a method for the volumetric determina- 
