I92I. No. 8. ox THE ECLOGITES OF .NORWAY. 13 



of FeO combined with a determination of réfringence as a conclusive 

 diagnostic of garnets. 



When the specific gravity can be determined, e. g. with the Clerici 

 solution and a Westphal balance, Ford's triangle-diagrams mav be used 

 directlv to determine the composition of the garnets. According to my 

 experience with the rock-making garnets, no greater accuracy can be 

 achieved by this method than by merely using the above refraction dia- 

 gram, but it may, of course, be useful to check these results. 



