34 



WORK OF THE PASADENA LABORATORY. 



The value of laboratory work in the interpreta- 

 tion of solar phenomena has already been illus- 

 trated. Magnetic fields are detected by the split- 

 ting and polarization of spectrum lines, differences 

 of temperature by changes in their relative inten- 

 sities, differences of pressure by shifts in their 

 positions, etc. By producing such effects artifi- 



FIG. 27. Pasadena Laboratory. 



daily, with the aid of powerful electric furnaces, 

 pressure pumps, and other physical instruments, 

 we can imitate a great variety of celestial phe- 

 nomena and interpret complex and obscure pecu- 

 liarities. It is thus plainly apparent that a phys- 

 ical laboratory is a necessary adjunct of an astro- 

 physical observatory. Our experience has shown 



