NOTES AND NEWS. 211 



essential constituent in it, so that its composition is clearly more 

 'acid.' As usual the mica makes a greater show on hand-specimens 

 than is warranted by its actual quantity. 



The microscope shows the following original minerals in order of 

 crystallisation : apatite, magnetite, biotite, plagioclase, quartz, and 

 orthoclase. Apatite, as usual in rocks of this family, is fairly abundant : 

 it forms longish colourless prisms, with characteristic cross-jointing, 

 and also very fine needles. It gives ' straight extinction,' or in other 

 words, is dark between crossed Nicols when the length of the crystal 

 is parallel to either of the cross-wires of the microscope. The slides 

 show some original magnetite in black opaque crystals, doubtless 

 octahedra. The brown mica (biotite) is for the most part decom- 

 posing into a green chloritic substance, with a separation of finely 

 granular secondary magnetite, easily distinguished from the original 

 crystals of that mineral. 



The felspars are much destroyed, but many crystals still show the 

 fine twin-striation of plagioclase, with low extinction-angles denoting 

 one of the more acid varieties. Other crystals appear to be ortho- 

 clase, and it is to be noticed that these latter sometimes mould round 

 the quartz grains, showing them to be of posterior formation to that 

 mineral. In some places, again, a micro-pegmatitic intergrowth of 

 quartz and orthoclase indicates a simultaneous formation of these two 

 minerals as the final stage of the consolidation of the rock. 



Besides feebly polarising green chloritic matter, radiating bundles 

 of brightly polarising epidote crystals occur among the alteration 

 products ; and also patches of calcite showing the characteristic 

 strong cleavage -traces and moderately weak polarisation -tints, the 

 double refraction of calcite being too great to cause bright colours in 

 slices of ordinary thickness. Further, some part of the quartz seen 

 in the rock is of secondary origin, and this may sometimes be 

 seen to have been deposited upon original quartz grains in crystalline 

 continuity with them. 



NOTES AND NE1VS. 



Mr. William West, F.L.S., of the Bradford Technical College, has a paper on 

 1 Desmids from Massachusetts' in a recent number of the Royal Microscopical 

 Society's Journal — with two plates — in which some new species are described. 



Vco< 



In the 'Tall Mall Gazette' for the last day of the old year appeared a 

 thoroughly sympathetic and appreciative notice of the incalculable service which 

 Mr. John Hancock has rendered to science in Newcastle-on-Tyne. 



An appointment of interest to Leeds naturalists is that of Mr. Henry Crowther, 

 who, while Assistant-Curator at the Leeds Museum, was one of the four con- 

 chologists who founded the ' Conchological Society' in 1876, to the curatorship of 

 the Museum at Truro, in Cornwall. 



July 1889. 



