300 NATURE'S TEACHINGS. 



coloured, while coloured liquids threw totally different bands, 

 irrespectively of their own colour. 



For example, the green colouring matter of leaves, called 

 chlorophyll, throws a single broad band on the extreme left 

 i.e. across the red part of the spectrum so far back, indeed, 

 that it is not easily seen at first. 



Then, suppose that we make some pale solutions of red sub- 

 stances, such as carmine, magenta dye, port wine, logwood, 

 permanganate of potash, and blood, it is possible to have them 

 so exactly resembling each other that not even the microscope 

 can discriminate between them ; yet the Spectroscope instantly 

 detects the colouring matter of each solution. 



The instrument is, therefore, invaluable in detecting adul- 

 terations of wine. For example, supposing that red wine is 



A a B C 



SPECTRUM OF SUWLIOHT, OB SOLAB SPECTKUM. 



SPF.CTP.UM OP BLOOD. 



suspected of owing its redness to logwood, and not to the 

 genuine grape, a drop is mixed with water and viewed through 

 the Spectroscope, which instantly tells whether the colouring 

 matter is grape or logwood. And as, by photography, the 

 spectrum can be exactly copied, an indelible record is procured 

 of the true nature of the object. 



So marvellously delicate is the instrument with regard to 

 blood, that it detects the thousandth part of a grain of colouring 

 matter in a blood-stain. 



If upon the spectrum were printed the word BLOOD in the 

 largest and blackest of capitals, it could not be more legible to 

 an ordinary reader than are the two blood-bands to the eye of a 

 spectroscopist. There is nothing like them in nature, and 

 whether it be by association of ideas, or by absolute fact, these 

 two bars have a strangely menacing look about them. Not 

 only that, but if the blood should be that of a person suf- 

 focated with carbonic acid gas, the Spectroscope will say so. 



Some years ago a man owed his life to the Spectroscope. A 



