'398 Scientific Intelligence. 



Thus (to indicate roughly the principles used), taking three 

 Maxwell's discs, a red, given and blue, so as to reproduce white, 

 we note the three corresponding ordinates at the earth's surface 

 spectrum, and comparing these with the same ordinate- in l lie 



discs, so as to give tin' proportion of red, green and blue which 

 would he seen tin,;, and obtain by their revolution a tint which 





[. Geology and Natural History. 

 mtions to Mineralogy ; hy F. A. Git 

 Lviitly published some new observations hi 



see\his7onrnal, vi, 461). The' cases no 

 5: (1) Corundum altered into */>i at/. At 



