CHAPTER II. 



TRANSMISSION SPECTRA OF DIFFERENT MINERALS. 



GROUP I: MINERALS CONTAINING WATER OF CRYSTALLIZATION. 



All the minerals studied which are generally thought to contain 

 water of crystallization are collected in Group I. First of all, it will 

 be necessary to consider the absorption spectrum of water, which has 



WO? 



I Z 3 4 56789 



FIG. i. Water. 



been studied by Julius, 1 Paschen, 2 Aschkinass, 3 and others. All observ- 

 ers agree in their location of large absorption bands at the approximate 

 wave-lengths 1.5 /*, 3 /*, 4.75 /*, and 6 p. 



1 Julius : Verhandl. Konikl. Akad. Amsterdam, Deel I, No. I, 1892. 

 'Paschen: Ann. der Phys. (3), 53, p. 334, 1894. 

 'Aschkinass: Ann. der Phys. (3), 55, p. 406, 1895. 



2 c 17 



