2p2 MR. H. H. ARNOLD-BEMROSE ON [Aug. I907, 



hard basalt. Small blocks of this basalt are spread over the 

 country in the immediate neighbourhood, some at a greater height 

 than the summit of the hill. This travel of the blocks is probably 

 due to ice-action, and their presence in other districts of the 

 county farther sonth has enabled Mr. E. M. Deeley and myself to 

 trace the path of the ice through: parts of the uplands of Derbyshire. 

 In a hand-specimen the basalt is easily recognized by its fresh 

 appearance, hardness, closeness of grain, and by the presence of 

 small nests of a bottle-green olivine. Fifteen thin slices of the 

 massive rock from various parts of the hill were examined ; it 

 is a typical oli vine-basalt, in which all the minerals are in a 

 remarkably-fresh state of preservation. The olivine occurs in 

 phenocrysts and groups, in small prisms and in irregular grains. 

 The felspars occur generally as small laths showing a well-defined 

 floW-structure, but in several specimens two generations are seen. 

 Magnetite and interstitial or glassy material are also present. The 

 following is a brief description of some of the thin slices. 



Nos. 76 & 105. 1 — The rock consists of numerous phenocrysts of olivine and augite, 

 in a groundmass of lath-shaped felspars which exhibit well-marked flow- 

 structure, augite in small granules, magnetite, and an isoti*opic glassy 

 material. Both the olivine and augite occur in isolated crystals, and in 

 groups of crystals or nests. The augite possesses zonal and hour-glass 

 structure, is often corroded at the edges, and sometimes contains portions 

 of the glassy groundmass. The biggest augite-crystal is T5 mm. in 

 length, and the felspar-laths attain a maximum length of '16 millimetre. 



No. 721. —Contains a, nest of olivine and augite measuring 2*7 X 22 milli- 

 metres. 



Nos. 717, 722, & 724. — In these specimens the augite-phenocrysts are absent. 

 The rock consists of phenocrysts of olivine in a base of felspar-laths, 

 magnetite, and small augite-prisms, with glassy material. 



Nos. 93, 95, & 96. — Contain olivine- and augite-phenocrysts, granular augite, 

 felspars of two generations, magnetite, and interstitial material. 



No. 720. — Olivine and augite are present as phenocrysts. The augite occurs 

 also in small prisms and in grains. The felspars are small, and show 

 fluxion-structure. 



No. 345. — Is very rich in small olivine-phenocrysts down to *05 millimetre in 

 length, which occur in a groundmass of small felspar-laths, augite-prisms 

 and grains, and magnetite, with a very small quantity of interstitial 

 matter. The felspar-laths form by far the greater portion of the thin 

 slice. ■ 



No. 106. — Contains small olivine- and augite-phenocrysts, with big augite- 

 grains. One of the felspar-laths is 3 millimetres long. 

 Pour specimens of the agglomerate were examined. 



No. 723. — Consists of a crystalline limestone, with foraminifera and other 

 organisms and a few glassy lapilli. 



No. 989. — Is a limestone rich in foraminifera and Calcisph&ra. It contains 

 glassy lapilli, and has been more or less marmorized. 



Nos. 990 & 1132.— Are similar to the preceding, and contain vesicular lapilli. 



1 These numerals correspond to the numbers of the microscope-slid t 

 the Author's collection. 



