The Microscope. 69 



modifications have been studied and are known, and are as much 

 signs of recognition as the regular spectra are. 



One of the most practical results in metallurgy shows the high 

 value of the prismatic test. The examination of the spectrum of 

 carbon has led to a revolution in the manufacture of Bessemer 

 steel. Formerly it was veiy difficult to determine at what precise 

 moment the oxygen of the air had burned out the carbon and 

 the silicon, a process necessary to produce an excellent steel. 

 Experts who watched the flame and could ascertain by long expe- 

 rience, with more or less exactitude, when the proper moment had 

 arrived, were few and expensive. To ^the uninitiated no difference 

 of the flame is visible. By the aid of the spectroscope this differ- 

 ence can be made out with the greatest ease and exactitude. 

 A cursory inspection of the flame spectrum and its various phases 

 reveals a certain number of absorption bands and bright lines, and 

 informs us of the exact moment when the iron mass has been 

 converted into excellent steel, when the admission of air and its 

 oxygen is stopped immediately, and the process is finished, with 

 invariable good results. The spectrum of Bessemer steel may be 

 examined in the work of Henry E. Roscoe, second edition, p. 164. 



THE SPECTROSCOPICAL ANALYSIS OF THE BLOOD. 



In the past, and before the spectroscope had entered into the 

 service of medicine, the microscope was to a great extent relied upon 

 to demonstrate the presence and changes of blood. At the same 

 time the chemical arsenal was ransacked to furnish reactions for the 

 detection of traces of altered blood. Whoever ponders over the 

 painfully tedious and oftentimes faulty proceedings devised and 

 carried out for this purpose, will not fail to hail and appreciate the 

 modern methods of investigation. Chemical analysis is difficult, and 

 often impossible with very minute traces of blood. The microscope 

 can demonstrate blood only within comparatively narrow limits. 



So long as the blood-corpuscle can be obtained, and if it is a 

 solitary one only, if well defined, the presence of blood can be made 

 out; but when, by some chemical or other means, the cell form of the 

 blood-corpuscle has been destroyed, when by a process of disintegra- 

 tion every trace of its contour and outline has disappeared, when it 

 has lost all characteristics of blood, and is only presented to us in 

 extremely minute proportions, as an amorphous substance, or as a 

 coagulated, physiologically altered pigment, or in an offensive and 

 putrid mass, then the highest magnifying powers of the microscope 



