W. M. Hutchings — Ash-slates of the LaJxe- District. 159. 



occurs, both by itself and in mixture with coarser matter, quite free 

 from garnet-grains, but in other respects exactly the same as just 

 described. An example of this may be taken from the old quarries 

 at the top of Kentmere Valley, a little below the reservoir. Some 

 of the slates here are of the utmost fineness and smoothness and in 

 outward appearance could not be distinguished in any way from 

 some Welsh sedimentary slates. 



The microscope- shows the same intimate mixture of chlorite, mica, 

 and ultra-fine quartz-mosaic, but free from garnet. A sample 

 prepared as before was analyzed by Mr. Paterson with the following 

 results : — 



(Ferrous oxide not determined.) 



100-11 



We see here that silica is in still greater abundance, and that soda 

 has not so fully disappeared, which perhaps partly corresponds to 

 the fact that some few small grains of clastic felspar are still dis- 

 cernible in the specimen from which this analysis was made, the 

 material having been a trifle coarser than the Mosedale specimen, in 

 which no such grains now remain. The soda may also be here 

 partly in the mica, or there may be also regenerated felspar in the 

 mosaic. 



The above two occurrences of fine-grained slate were selected 

 partly for the reason that from among many examined they Seemed, 

 on microscopic examination, to be the most highly micaceous and 

 most completely altered, and the subsequent analyses bore out this 

 selection. Another instance may be given of a very fine-grained 

 slate (from a quarry at Grasmere), which gives chemical results 

 differing considerably from the former ones. Under the microscope 

 just the same things are seen as in the Mosedale slate. It differs in 

 containing more chlorite and a good deal of finely-disseminated 

 calcite ; and it is rather less micaceous. After extraction with 

 acid and potash as before, just the same sort of material remains 

 behind, the garnets being rather larger than at Mosedale. 



A sample .was prepared, half of which was extracted as before, 

 and the original and extracted portions were taken by Mr. Paterson 

 for determination of silica and alkalies, the following figures being 

 obtained : — 



A. Original. B. Extracted, 



Silica = 61-75 per cent. 77 "40 per cent. 

 Potash = 0-85 „ ) «.,. „ „ 2-40 „ 1 , „- 



Soda = 5-49 ,; )6-34p.c. ^.g^ ^'^ j 7-27p.c. 



Looking first at analysis B., we see that a very large amount of 

 soda is present as compared with the Mosedale and Kentmere cases. 

 The potash-percentage is not very different from that at Kentmere. 



