Professor Bonney — On Limhurgite from Sashach. 413 



that I might either go there myself (it is now more easy of access) 

 or get a friend to ascertain the actual relation of this to the more 

 familiar variety of limburgite. Last Spring, Mr. P. Haas, B.Sc, 

 one of my former students at University College, informed me that 

 he proposed attending lectures at the University of Freiburg, so 

 I asked him to visit Limburg. Early in the Summer he forwarded 

 to me a small box of specimens and a rough sketch of the quarry, 

 on which the position of each was marked, and of which I annex 

 a copy. This quarry, Mr. Haas informs me, is on the south side of 

 the hill marked by the ruined castle of Limburg, near the south- 

 eastern angle ; the one from which Professor Rosenbusch obtained 

 and described specimens being on the north-west side, near the ruin 

 and overlooking the Rhine. 



A. 

 B. 

 C. 

 D. 



Fig. 1. 

 Upper flow, limburgite (inaccessible). 

 Upper tuff. 



Middle flow, limburgite. 



Lower tuff, much foreshortened, with path on clifi edge. All this is covered by 

 slipped-down loess, but Mr. Haas saw the tuff at D and in two places near 

 D', where also limbiu-gite was exposed in two places (2 marking one of 

 them) , and the relations of the lava and tuff appeared to be irregular here. 

 E. Lower flow, limburgite. 

 L. Loess, often slipped. 



The numerals indicate the positions of the specimens described in] the text, 

 5 being the dark rock. 



It will save time to arrange the specimens for description 

 according to their structure rather than their situation in the mass. 

 The first (1) has a general resemblance to a specimen (purchased) 

 which has been in my collection for some five and twenty years, 

 except that its vesicles are a little smaller and more thinly lined 

 with (white) secondary minerals.^ There is a slight but unimportant 

 difibrence in the tint of the groundmass, and the visible crystals of 

 augite are a little smaller. Microscopic examination proves the 

 larger crystals to be imbedded in a matrix consisting of small 

 elongated prisms of brownish augite, with a few rods of iron oxide, 



' I have a couple of slices of limburgite, bought nearly as long ago. Thev show 

 the usual minerals, imbedded in a rich brown glass, in which also are scattered a few 

 microliths, apparently a pyroxene. 



