FREE INSTITUTE OF SCIENCE 



71 



ETHER WAVES AND THE MESSAGES THEY BRING ' 



the bell as soon as the spark is discontinued. In this way the ringing of the 

 bell can be controlled by a person operating the sparking apparatus. The 

 Morse code may be represented by a suitable arrangement of long and short 

 rings. 



If, when a solar spectrum is thrown on the screen, a photographic plate is 

 placed beyond the violet end of the spectrum, it will be found that the plate is 

 quickly affected. This fact reveals the presence of waves shorter than those 

 we call violet. They are called the ultra-violet waves. They are always 

 produced at very high temperatures, and may easily be obtained by passing a 

 violent electric discharge through a body of gas at low pressure. The Cooper- 

 Hewitt mercury vapor lamp produces them in large quantities. These waves 

 were extensively studied by Draper, Stokes, Cornu, and others. It soon be- 

 came apparent that the greatest difficulties in connection with their study lay 

 in the fact that they are absorbed by comparatively thin layers of glass or even 

 of air; therefore, they must be studied in a vacuum if satisfactory results are 

 to be obtained, and with lenses and prisms of some other material than glass, 

 usually quartz, or better still, fluorite. In the extremely short lengths, Lyman 

 has been very successful in replacing both lenses and prisms by a concave re- 

 flection grating. The men I have mentioned first extended our knowledge of 

 the ultra-violet to about wave length 2000. Then very little additional was 

 done until Schuman took up the work. Our accurate knowledge of this region 

 is due largely to the work of this one man. His results were so remarkable and 

 were obtained under such conditions as to make appropriate a few words con- 

 cerning him. He was born near Leipzig in 1841, and was educated as an 

 engineer. He engaged in the business of manufacturing machinery for book- 

 making. He continued in this business until 1892. He was unable to engage 

 in scientific work until after he was forty years of age. Even then his in- 

 vestigations were carried on in the evenings and at such other moments as 

 he felt he could spare from his profession. He was never wealthy, and most of 

 the proceeds of his day's work was devoted to his investigations. Under his 

 persistent application his health was undermined and his eyes became seriously 

 affected. In 1903 he was forced to give up all experimental work and in 19 13 

 he died a martyr to science. He instituted the method of working in a vacuum 

 and substituted fluorite for prisms and lenses. He extended the spectrum to 



o 



about the region of 1250 Angstrom units, and studied the properties of the 

 region to this point very thoroughly. 



