500 Chronicles of Science. [ July, 
The feeble striping of the glass surface thus obtained produces accu- 
rately the condition of a series of lines crossing at an angle of 60°, 
which is fulfilled by the similarly directed edges of the groups of 
microscopic crystals observed in some kinds cf mica, &c. By cutting 
the glass to the shape of any other regular sided figure, and rubbing 
it with emery-paper in directions parallel to the different sides, an 
eight-, ten-, or multi-fold star will be produced, according to the 
angle under which the series of lines cross. These are best observed 
by holding the glass near the eye, and looking at a fine hole in a plate 
of metal behind which a candle-flame is placed. 
A new analysis of Fraiinhofer’s line D has lately been communi- 
cated to the Royal Society by Mr. Gassiot. The spectroscope with 
which it was performed was made by Browning, and is, without 
doubt, the most magnificent instrument of the kind which has ever 
left the workshops of that optician. The train consists of no less 
than eleven bisulphide of carbon prisms, the sides of which are pre- 
pared by Professor Cooke’s method, so as to remedy the curvature of 
the glass-plate from the hardening of the glue. On examining the 
double line D, after passing through this train, it was found that its 
two components were separated 3/6”, and that there was a third line 
exactly equidistant between them, together with other lines, filling 
up the intermediate space. But the most remarkable circumstance 
was, that the two dark lines composing the double line, were them- 
selves each split up into three lines, the centre one being the thickest. 
It is intended to examine other parts of the spectrum with this appa- 
ratus, and there is no doubt that very valuable results will be obtained 
from such an extended investigation. 
Spectrum analysis is not only applicable to the detection of 
metallic elements. By a slight modification of the apparatus, this 
powerful agent may be applied to the discrimination of a vast number 
of organic bodies; hitherto, however, this branch of the subject seems 
to have been unaccountably neglected, Professor Stokes being almost 
the only person who has assiduously devoted himself to the subject. 
One of the most recent results at which he has arrived is likely to 
be of considerable practical importance. He has submitted blood to 
searching spectrum analysis, both before and after treatment with dif- 
ferent chemical re-agents. This liquid exhibits two well-marked dark 
bands in the yellow and green. ‘These were first noticed by Hoppe, 
and -are eminently characteristic of blood. The addition of an 
alkaline solution of copper to this fluid still shows these characteristic 
bands, although to the eye the colour is quite changed. On adding, 
on the other hand, acetic acid to a solution of blood, the colour was 
very slightly changed, but the bands had entirely disappeared. A 
comparison of these bands with those given by some iron salts, nega- 
tive the supposition that the colour of blood is due to a salt of iron, 
as such, even had we no other means of deciding. 
In a note by M. Marignac, on silico-tungstic acid, he describes a 
remarkable series of compounds, most of their properties, however, 
