The Microscope. 43 



information, by reaction for every alteration that blood undergoes 

 when acted upon by poisonous gases, and those of minerals or other 

 destructive agencies, and it is a powerful means to unravel the secrets 

 of crime. A^'ell may we say, "no medical man can claim to stand 

 at the heiffht of medical culture who is ignorant of the results of 

 spectrum analysis." 



HISTORICAL. 



Our account of the rise and progress of spectral analysis must 

 be brief, although it is full of intrinsic interest, the space allotted 

 to me forbidding a fuller and ampler detail. Sir Isaac Newton may 

 be justly called the father of spectroscopy. He discovered, or first 

 saw the spectrum in 1675 ; he promulgated then his masterly and 

 imsurpassed prismatic theorems. He grappled with the subtle ques- 

 tion of light, and his emission theory, although disproved in our days, 

 stands out yet as the bold and ingenious structure of a giant mind. 

 He darkened his room, made a round hole in the shutter of the window 

 and allowed a sunbeam to cross his room. This beam he intercepted 

 with a prism, and had the inexpressible pleasure to see the beautiful 

 spectrum, the colored band containing all the tints of the rainbow in 

 exquisite beauty and splendor. But his discovery was barren in 

 practical results. The way the sunlight entered Newton's room pre- 

 vented him from seeing the sunlines, which, in our days, have become 

 the means and landmarks of remarkable discoveries. Instead of a 

 round hole we now use a narrow slit that prevents the over-lapping of 

 the sunrays and makes the observation of the sunlines possible. In 

 1752, Melville experimented with colored flames. Pierre Prevost 

 wrote on the identity of heat and light. Wollaston discovered 

 the dark sunlines in 1802, but he failed to make any practical appli- 

 cation of his important discovery. In 1814 Frauenhofer, of Munich, 

 used, examined and studied these lines more thoroughly. He 

 mapped and named the most prominent of them with the letters of 

 the alphabet from A to H, and used them as standards for measure- 

 ment, and to this day, they are known as the Frauenhofer^ s sunlines. 

 He also examined the light from the moon and from Venus, and 

 found the same spectral lines at the same distance from each other. 

 He observed that in Sierius, in Cygni, and in Capella, the arrange- 

 ment of dark lines differed from those observed in the sun, and he 

 concluded that these lines were caused by some absorbing power in 

 the sun and in the stars. 



But the deep importance and origin of these lines remained 

 undiscovered until up to a very recent period. In 1861 Sir David 



