MODERN SCIENCE. 249 



composed of either two or three telescopes mounted on 

 one foot, and whose axes converge towards a prism or a 

 series of prisms, each of which more and more spreads the 

 light coming through one of the telescopes, and causes its 

 spectrum to fall in a high degree of purity on an object 

 glass. Saving a very considerable amount of labour and 

 time, it immensely facilitates chemical manipulation; for 

 investigations which would demand the repetition of the 

 same experiment perhaps twenty times so as to give an 

 average result, and employ as many days, can be carried 

 out within a few hours 3 time. Not the least precious value 

 of the instrument lies in its excellence as a means of 

 verification of much laboratory work. We may here point 

 out that, so far, we are in possession of five processes of 

 chemical analysis* or manipulation; each, except the last, 

 divided into sections according as you want only to discover 

 what the constituents of a compound substance are, in 

 which case the analysis is called qualitative, or to determine 

 also in what proportion the constituents are exhibited, in 

 which case it is called quantitative analysis. The five 

 methods are : i, the process of Geber (800) distillation, 

 supplemented by the analysis of the products ; 2, the testing 

 process precipitation, due to elective affinity Bergmann's 

 system (1761) ; 3, Electrolysis decomposition by electricity 

 Davy's process (1806); 4, the blowpipe process fusion, 

 by means of a fierce flame the development of which is 

 due mainly to Berzelius (1818); 5, lastly, spectral analysis 

 by means of the spectroscope due to Fraunhofer (1814), 

 and to Bunsen and Kirchhoff (1860). By these various 

 methods have the SEVENTY-TWO SIMPLE ELEMENTS known 

 been discovered the seventy- two elements, that is, which 

 constitute the material universe, so far as we have ascertained 

 at present. Qualitative analysis is carried on principally by 

 flame tests and liquid tests, of which there are numberless 

 varieties, and also by the use of the spectroscope, par- 



* It should be remembered that, strictly speaking, analysis is the 

 name given to the decomposition of a compound into its elementary 

 parts, just as the name synthesis is given to the process of forming a 

 compound out of two or more elements. 



