ON THE CONSTRUCTION AND USE OF THE 
SPECTRUM - MICROSCOPE. 
BY H. C. SORBY, F.R.S. 
E VERY one is in the constant habit of distinguishing differ- 
ent objects by their colour. In many cases this is sufficient 
to characterize various small bodies seen with the microscope. 
Now, strictly speaking, spectrum analysis is nothing more than 
a refined and scientific method of applying the same principle, 
and the spectrum microscope is simply an instrument which 
enables us to employ it in the case of very small objects. It is a 
more refined method, because we may have a number of different 
substances so nearly of the same colour, that it would not 
enable us to tell one from another ; and yet, when examined 
with a spectroscope, their spectra might be entirely different and 
quite characteristic. On the contrary, we may have cases 
where the presence of foreign colouring matter so entirely 
disguises the natural colour of a substance, that its presence 
would scarcely be expected; and yet, when examined with a 
spectroscope, the spectrum may be so characteristic, that 
its presence is perfectly well established. In these remarks I 
refer to coloured solids or liquids. The spectroscope has been 
so commonly restricted to the examination of coloured 
flames — i.e., to the study of the light given off from incan- 
descent vapours — that I have found many persons who believed 
that in order to obtain the spectrum of such substances as 
blood, it is requisite to burn it. There can be no doubt what- 
ever that, on the whole, the facts to be learned from the study 
of mineral matter in the state of incandescent vapour are far 
more important and decided, because the spectra are far more 
characteristic ; but still we may learn a number of valuable 
facts in studying the light transmitted or reflected from solid 
or liquid coloured substances. 
In this communication I purpose first to describe what I con- 
sider to be the best form of instrument ; and then, after some 
general remarks, to give a few hints on the preparation of 
objects for examination ; and conclude with the description of 
some characteristic examples. 
