122 W. M. Huichings — An Interesting Contact- Roch. 



grand vus, Heer, but which belongs to a new genus of Apidge, in 

 which the neuration more closely resembles that of Eucera. 



EXPLANATION OF PLATE VI. 



Fig. 1 . Drymadusa speciosa, Heer, sp. ; male fore-wing f . 



Fig. 2. Acridium CEitingense, sp. uov. ; fore-wing f. 



Fig. 3. Stenolestes iris, Heer, sp. ; outer portion of fore-wing f-. 



Fig. 4. Calosoma Heeri, sp. nov. ; elytron x. 



Fig. 5. JSfecromyza pedata, sp. nov. ; -^. 



IV. — An Interesting Contaot-Rock, with Notes on Contact- 



Metamorphism. 



By "W. Maynakd Hutching*, F.G.S. 



FOR a considerable time past I have been engaged, in collaboration 

 with Mr. E. J. Garwood, in an investigation of the rocks in 

 contact with the Whin Sill. The results of our joint work, geological, 

 petrographical, and chemical, will be published in detail in due 

 course. In the meantime there are some special observations, made 

 on some of the rocks in question, which have more or less bearing 

 on some of the points dealt with in a paper 1 contributed to the 

 Geological Magazine last year (Geol. Mag. 1894, pp. 3.6 and 64). 



These observations having been made since that paper was pi'inted, 

 I have thought that it may be worth while to give an account of 

 some of them, more especially as regards an interesting bed of 

 altered shale which occurs at Falcon Glints. It is at this locality 

 that the contact-action of the Whin Sill is very stinkingly developed, 

 there being an exposure showing fine garnet-limestones and other 

 altered rocks. The bed in question is 75 feet below the contact, 

 from which it is separated by a series of layers of limestones, 

 sandstones, and shales, all altered. It is 8 feet thick, and rests on 

 the basement conglomerate of the Lower Carboniferous. 



It is for the most part a darkish gray, compact rock, with no 

 remaining fissility. Its appearance is in many respects like that of 

 some felsites. Its most striking iBacroscopic characteristic is that 

 it contains large numbers of spherical, and approximately spherical 

 bodies, like peas, and of various sizes up to rather over half an inch 

 in diameter. These nodules are of a darker colour than the rock. 

 They are not at all evenly dispersed in it, being at some places 

 comparatively rare and scattered, while at others they are closely 

 packed, and in some cases touch one another. At some parts of the 

 rock they can be easily taken out unbroken, leaving perfect hollows 

 where they have been ; at others they are not in this loose condition, 

 and can only be got out in bits by smashing the specimen. This 

 difference is due to a slight weathering-action having, in some of 

 them, caused the formation of a less coherent skin between tiie 

 nodule and the containing rock. 



Microscopic examination shows that this bed is not quite uniform 

 in its nature throughout, and chemical tests confirm this. Thicker 

 beds of shale or clay in the Carboniferous are nearly all found to 

 vary in nature, as successive laj'ers contain varying pi'oportions 

 of quartz aaid of fine clay-material, so that their chemical com- 



