574 Reviews. [July, 
scope is its excessive delicacy. It is hard, sometimes, to tell whether 
the spectrum seen is given by the material under examination, or 
whether it is not caused by minute portions of the substances floating 
in the atmosphere. It is for this reason that M. Grandeau insists 
strongly upon the necessity for a scparate and distinct laboratory in 
which to carry on spectrum investigations. This laboratory, he adds, 
should be provided with the means of effecting a thorough ventilation, 
so as to get completely rid of volatilized matter. 
The author also points out the advantage of securing a room with 
a southern aspect, the window of which can be darkened with wooden 
shutters, a circular hole in one of which may admit a beam of solar 
light for examination and comparison. 
No less useful to chemists beyond the reach of gas, is the hint that 
in the absence of a Bunsen’s jet the best source of heat and light to 
employ is a lamp fed with wood spirit. It is also very properly pointed 
out that when either such a lamp or a common spirit lamp is em- 
ployed, the brass collar through which the wick passes should be well 
platinized to prevent the appearance of the spectrum of copper, some 
of which metal is always carried along by the spirit. 
The spectrum of copper is rather complicated, but it may mislead 
a young experimenter, who would, however, be able to set himself right, 
if he checked his results with the spectroscope by an ordinary 
chemical analysis. And here we may mention what M. Grandeau 
calls a most happy coincidence. It is the circumstance that those 
substances which are most difficult to detect by purely chemical means, 
are just those which give the most simple and characteristic spectra. 
Take as an illustration the fact mentioned in our Chemical Chronicle. 
Plattner had a large amount of cesium in his hands, and yet failed 
by chemical means to discover that it was anything different from 
potassium. Bunsen had a very minute proportion, but instantly recog- 
nized in the two blue lines the sign of something new. How minute 
a proportion of some metals may be discovered is stated by the author, 
and we quote his statement without, however, guaranteeing the accu- 
racy of the determination. He says, that the observation of the 
lines of the spectrum enables us to prove most distinctly the presence 
of 0:000,000,3 of a milligramme of sodium, and 0:000,000,9 of a 
milligramme of lithium ! 
The exact value of the spectroscope in analysis is, as we have 
hinted, yet to be determined, but the value of the results already 
arrived at by its means are unquestioned. Four new simple bodies 
have been brought to our knowledge in the same number of years, a 
result unprecedented since the time of Davy ; and although a chemist 
can hardly wish the mumber of simple bodies to go on extending at 
this rate, we hope there is yet a rich harvest to be reaped to reward 
the labours of other observers. 
We have already expressed a warm commendation of this book, 
which we have only to add extends to every part but the chromo- 
lithographs at the end. If anyone should arrange for its translation 
into English, he had better get fresh plates executed. 
