90 MR. E. E. WALKER ON THE GARNET-HEARING [.Feb. I904, 



Crag and the lower slope of Bell Rib, Yewbarrow, also in the 

 intrusive sill just mentioned as occurring in itosthwaite Fell. 

 In the last rock the lines are often separated by several inches. 

 Quartz, calcite, chlorite, and ilmenite are found, the two first 

 occupying the centre of the vein. The rock in close proximity to 

 the vein takes on a speckled and dirty appearance, due to the 

 dissemination of minute chlorite-flakes. Again, fault-planes are 

 a determining factor. An example of this kind has already been 

 instanced in the case of the Blea-Crag rocks, where epidote and 

 chlorite have been introduced along what might be termed ' planes 

 of lag-faulting.' In the ' streaky ' rocks proper infiltration has taken 

 place most frequently along the bedding-planes ; but veins produced 

 along fault-planes do occur, crossing the bedding-planes at all angles. 



Very often the infiltrated products assume a lenticular shape. 

 This is well shown by the greenish rocks of Whelter Crag (Hawes- 

 water). Dark -green lenticular patches are developed in a light- 

 green rock, with felspar-phenocrysts. These dark-green patches 

 consist of chlorite and calcite, sometimes accompanied by quartz ; 

 a discoloration in the rock-matrix surrounding these patches is due 

 to the dissemination of minute chlorite-flakes (3802). The rock 

 presents the character of a rhyolitic ash, and the infiltrations 

 may be very similar in origin to that of quartz in rhyolites. 



More rarely, infiltrated chlorite occurs in the same way as in- 

 trusive veins, penetrating a rock and enclosing fragments broken off. 

 These fragments have chlorite introduced along the bedding-planes 

 or other planes of weakness, and a 'streaky' character is thereby 

 given to them. A good example of such action is afforded by a 

 loose block found on the slope of Mickle Moss in the Hawes- 

 water district, and these phenomena may be seen in Slide 3817. 

 The rock is a pinkish-white rhyolite, showing phenocrysts of 

 orthoclase in a felsitic groundmass, with irregular felspar-patches. 

 The chlorite occurs irregularly, either in long patches or in minute 

 veins cutting across the felspars, and occasionally replacing them by 

 chlorite-pseudomorphs. Another example of a mass of chlorite 

 behaving as an intrusive rock is afforded by banded ash, near the 

 junction of the streams from Bleawater and Smallwater Tarns in 

 the Haweswater district. 



We might expect to find a similar ' streaky ' character : 



(2) As the result of lamination in fine fragmental rocks ; 



(3) As the result of flow of igneous material; 



(4) As the result of dynamic action on included fragments. 



It may be stated at once that all four types of structure can 

 be found, and that it would be impossible to ascribe all ' streaky ' 

 structures to one origin. At the same time, it is a very difficult 

 matter to say definitely to which class a particular ' streaky ' rock 

 belongs. 



With regard to the distribution of ' streaky ' rocks, they are 

 generally found in a zone between the Eycott Lavas and the typical 



