28 INTRODUCTORY ADDRESS: 



point used is practically sharp under a magnification of no less than 

 2000 diameters. By this method these combined characteristics can 

 be obtained for any individual crystal, a point of great importance. 



SECTION VIL— THE ULTRAMICROSCOPE. 



Much study has been given to the Ultramicroscope, which was 

 introduced about the year 1905 by Siedentopf and Zsigmondy. 



In an article which appeared in " The Scientific American," October 

 2nd, 1915, it was stated that the limits of microscopic observation 

 with direct illumination is about ^~^ mm. and with oblique illumina- 

 tion by means of violet rays and with the aid of monobromated 

 naphthalene immersion ^qoooq mm. The observation of particles 

 below this may be termed ultramicroscopic. According to Siedentopf, 

 particles may be perceived which have a diameter of about ^ qooooq 

 to ^ OOP OOP nim. These are magnitudes which approach very 

 closely to molecular dimensions of complicated compounds, in some 

 cases even attain them. 



According to 0. E. Meyer, the molecule of Hydrogen has a diameter 

 ^^ 10.000.000 ^"^-j ^^^^^ according to Jaeger, the molecule of (a) 

 ethyl-alcohol has a diameter of p^ ^ — mm. ; (b) chloroform has 



X 1 o.ooo.ooo ' ^ ' 



a diameter of ^-5-^^-^^ mm. According to Lobry de Bruyn, the 



molecule of starch has a diameter of ^ mm. Consequently 



. . 1 .000,000 ^ / 



the molecule of starch must be within the leach of ultramicroscopic 

 perception. 



The investigator has therefore before him, subject to increased 

 intensity of light and dark field, the possibility of seeing molecules 

 which seemed beyond reach of human sight, and the hope of following 

 the play of their attractive and repellant forces. The brightness of 

 ultramicroscopic particles begins to decline with the 6th power of the 

 diameter. 



If it should prove possible to obtain this deeper insight into the 

 form and structure of matter, a positive service will be done to philo- 

 sophy permitting of the observation of particles which were formerly 

 far below the limits of ordinary microscopic observation. If the 

 methods which it renders possible can be extended and applied to 

 Metallurgy, then the Metallurgist will doubtless be possessed of still 

 further means to enable him to advance further our knowledge of 

 the structure of metals and their alloys. 



SECTION VIII.— CONCLUSION. 



I must now bring these remarks to a close. The subject is a 

 fascinating one, and it has been a labour of love to trace the History 

 of the Microscope and its great development into the wonderful 

 Scientific Instrument of to-day, capable of resolving even over 

 100,000 lines per inch. 



