1892.] Mineralogy and Petrography. 853 
contain titanium, which of course must necessarily exist as widely 
spread in the rocks from which the soils were made. 
Small crystals of melilite have been detected by Bédliinder™ in a 
mass formed by the melting of Portland cement in an oven witha 
lining containing 63%-88% of SiO, The raw materials used as the 
charge consisted of a mixture of magnesia, limestone and clay. The 
crystals were imbedded in a mass of olivine(?), magnetite, mica and 
apatite. Thecrystals were found to be optically positive and to have 
the composition : 
SiO, AlO, FeO, CaO MgO K,O Na,O 
37.96 9.46 2.93 34.75 12.77 153 .64 
Becke” gives brief but very definite directions as to the use of his 
method of distinguishing between quartz, orthoclase and plagioclase 
by etching with hydrofluoric acid and staining their etched surfaces. 
Schrauf” describes a method of combining microscope and reflec- 
tion goniometer in such a way that minute crystals may easily be 
studied and measured. 
“Neues Jahrb. f. Min., etc., 1892, i, p- 53. 
` 3Min. u. Petrog., Mıtth. xii, p. 257. 
%Zeits. f. Kryst., xx, p. 90. 
