W. M. E'utchings — Ash-slates of the Lake- District. 219 



most of the andesites, etc., which can be collected in situ. Even in 

 some cases where the slates are most highly cleaved, and the "base" 

 and some of the other constituents, as chlorite and calcite, are drawn 

 into streaks often flowing round the still angular lapilli, these latter 

 have almost wholly escaped mechanical damage. In these cases of 

 strikingly good preservation basic lapilli are absent. The slates 

 from Mosedale quarry have already been mentioned as offering 

 beautiful examples of well-preserved lapilli, and equally good ones 

 are seen at other places. 



It is to be noted that though rhyolite is exposed in comparatively 

 few localities in the district, it is more or less represented in almost 

 every specimen of slate in which the lapilli are still distinct. This 

 frequent occurrence of rhyolite in the fragmental rocks of the Lake 

 District has been noticed also by Harker and Marr (On the Shap 

 Granite, etc.. Quart. Journ. Geol. Soc. vol. xlvii. 1891). 



In addition to volcanic lapilli, many of the slates and tuffs show 

 also the presence of fragments of sedimentary rocks, presumably 

 broken through and ejected by the explosive eruptions. I have 

 formerly recorded (Geol. Mag. 1891, p. 462) the occurrence of 

 such a mixed volcanic and sedimentary material in a tuff at Falcon 

 Crag. It may be observed again, though in less marked degree, in 

 rocks from Honister Crag, both roofing-slates and coarser tuffs and 

 breccias, in which fragments of grits and gritty slates occur ; and 

 in material from several other localities careful search shows that 

 fragments of ordinary sedimentary slates are present, recognizable, 

 among other things, by the rutile-needles contained in them. In 

 many cases these fragments are crushed and drawn out so as to be 

 almost incorporated beyond recognition with the volcanic material, 

 and it is most likely that, as might be expected, a large proportion 

 of the ashes and tuffs of the district contain more or less of the 

 sedimentary strata underlying them. 



Angular clastic grains of quartz, some of good size, are also 

 tolerably frequent, suggesting a derivation from some coarse-grained 

 acid rock, probably granite. 



None of the finer-grained slates, so far as my observations go, 

 contain any trace of augite or other ferro-magnesian mineral. These 

 are now represented entirely by chlorite, calcite, and some epidote. 

 Chlorite is always present in large quantity in the coarser slates, as 

 patches and rolled-out streaks, as well as in the minutely-felted form 

 in the base. Calcite is exceedingly abundant, disseminated as small 

 grains down to fine dust, or as larger grains and crystals. These 

 frequently contain fluid-cavities with bubbles, showing the con- 

 ditions of pressure, etc., under which this calcite was deposited. In 

 many slates the calcite is so plentiful that it very nearly obliterates 

 everything else except the chlorite, the rolled-out mixture of the 

 two appearing at first sight to make up nearly the entire rock. 



It is interesting to note that though the mineral changes which 

 have taken place in the finely-powdered ash-material of these slates 

 are in a most important point similar to those which have occurred 

 in the deposits to which we owe our fireclays and shales and most 



