FORENSIC MICROSCOPY. 133 



lines, which are due to the presence of the cooHng vapors 

 of metallic elements in the surrounding atmosphere, each 

 of which absorbs the light corresponding to its own 

 bright line spectrum. The Frauenhofer lines may be con- 

 sidered the shadows of the spectra of the metals in the 

 outer atmosphere of the sun. 



Obviously artificial light should be used for the micro- 

 spectroscope, since the Frauenhofer lines would intro- 

 duce a confusing element. When various solid and 

 liquid substances are placed on the stage of the micro- 

 scope, absorption spectra of the same general type as 

 that of sunlight are produced, although the dark bands 

 are wider and less sharply defined, this being more and 

 more the case as the thickness of the body is increased. It 

 is therefore desirable to examine layers of varying depth, 

 and this may be done by means of a cell made by cement- 

 ing to a slide a piece of heavy glass tubing cut off obliquely 

 so that it shall be 5 mm. deep on one side and 0.5 mm. 

 deep on the other. 



The application of the microspectroscope to the exam- 

 ination of various organic bodies has not yet been 

 developed to anything Hke its possible limits. It has 

 yielded interesting results in the study of certain anima L 

 and vegetable coloring-matters; but its chief use has 

 so far been in the detection of blood-stains, since the 

 red coloring-matter of blood produces characteristic 

 spectra.. Suspected blood-stains which are to be thus 

 examined may be treated with distilled water until a 

 reddish-brown solution is produced, when it is apparent 

 that haemoglobin has gone into solution. The liquid 



