230 Reports c& Proceedings — Mineralogical Society. 



The Dharwar schists of Mysore contain a widely extended series 

 of banded quartz iron-ore rocks, very similar to those of the Lake 

 Superior district, the origin of which has been the subject of much 

 discussion and is still very perplexing. Some of the earlier 

 American geologists considered them to be directly igneous in origin, 

 but these views are now discredited, and replaced by an interesting 

 and ingenious theory of chemical precipitation from liquids associated 

 with subaqueous lavas. The Lecturer suggested that some of these 

 rocks might be pegmatitic intrusions of quartz and magnetite, and 

 that some might be the metamorphosed relics of igneous rocks 

 composed largely of highly ferruginous amphiboles (such as 

 cummingtonite) or other chemically allied minerals. 



II. — Mineralogical Society. 



March 19, 1918.— W. Barlow, F.R.S., President, in the Chair. 



Professor E. S. Federov : "Graphical Operations with four 

 Independent Variables." Apropos of Bocke's suggestion of the use 

 of multi-dimensional geometry for such operations, with special 

 reference to the case of the chemical constitution of tourmaline, the 

 author remarks that he had already put forward a similar suggestion, 

 without, however, making use of imaginary dimensions. A system of 

 points is replaced by a system of vectors, and in this way, since each 

 end of a vector has two co-ordinates, a relation between four inde- 

 pendent variables may be expressed graphically. Different series of 

 vectors of the first order give rise to vectors of the second order, and 

 they in their turn to vectors of the third order. Certain special 

 cases were discussed. 



Professor E,. P. D. Graham: " Lattice -like Inclusions in Calcite, 

 from Xorth Burgess, Ontario." The calcite, which is almost 

 invariably twinned about e (0112), contains numerous fine needles, 

 arranged parallel to the edges of the rhombohedron e, of a hydrous 

 magnesium silicate, which chemical analysis showed to correspond to 

 the formula 5 Mg . 6 Si O2 . 4 Hg 0, which is usually assigned to the 

 mineral spadaite. Since the needles are only slightly acted on by 

 cold dilute acid, they remain behind in the form of a lattice on 

 dissolution of the calcite. Other included minerals are pyroxene, 

 quartz, titan ite, and pyrites. The source of the solutions which 

 supplied the magnesium silicate was discussed. 



Dr. J. W. Evans: "On Linear Rock-Diagrams." The different 

 types of linear or variation diagrams, in which the chemical con- 

 stituents of different rocks are represented by vertical distances, 

 were reviewed, and the use of modifications to indicate the probable 

 mineral compositions was proposed. Each rock is represented by 

 two diagrams. In the first, or alumina diagram, distances repre- 

 senting the molecular proportions of (1) the potash, (2) the potasli 

 and soda, and (3) the potash, soda, and lime in each rock are measured 

 vertically upwards in siiccession one above the other from the base- 

 line, and corresponding points for different rocks are connected by 

 continuous lines. At the same times distances representing (4) 

 the alumina, (5) the iron oxide, and (6) ,the magnesia are measured 



