HARDWICKE'S SCIENCE-G OSSIP. 



267 



burrows, they wonderfully assist their lepidopterous 

 colleague in the work of destruction. Their tunnels 

 are sufSciently large to admit an ordinary drawing- 

 pencil, and are carried through the trunk in the 

 most fantastic fashion, up and down, backwards and 

 forwards, round and round, till at last they lead to 



Fig. 170. MvLSk Beetle (Cerambyx moschatiis'), 



the surface, where the dull-looking larva turns into 

 the glorious beetle. I have but seldom seen them 

 on the wing. They prefer to crawl about the tree 

 within which they have lived so long, warming 

 themselves in the sunshine, and waving their 

 graceful horns. Not far from here, on the banks 

 of the Thames, there stands a row of willows, or 

 rather a row of trunks wliich once were willows, 

 but now, owing to the attacks of cossus, musks, and 



Fig. 171. End of Foreleg of ditto. 



a host of other wood-boring insects, they are but 

 wrecks in venerable decay. On these trunks last 

 year there swarmed an immense number of musk 

 beetles. I have taken or assisted to take nearly 

 two hundred specimens, and there were always 

 some collectors looking for them. It was difficult 

 to believe that such a number of larvse could ever 

 have found accommodation in the old trees ; and they 

 certainlyiWere not the only inhabitants, for to my 

 knowledge two dozen specimens of the Goat-moth 

 were taken at the same place. On these trees the 

 musks used to sit five or six together, with their 

 antennge in such a tangle, that, if they had been 

 trying to knot themselves together, they could 

 hardly have succeeded ^better. It was not easy to 



detach them from the bark, into which tliey dug 

 their hooked claws witJi great force, and then, 

 while one was endeavouring to root them up from 

 beneath, they would be off like a shot, and down 

 some unfathomable crevice. 



W Tor the accompanying illustrations I am indebted 

 to the pencil of my friend Mr. G. P. Smale, of this 

 place. 

 Blaekheath. Edward Lefeoy. 



PtOCK STRIATIONS. 



"jV/TY attention has recently been attracted to 

 ^^ " Notes on Structure in the Chalk of the 

 Yorkshire Wolds, by J. R. Mortimer, Esq.," a 

 short notice of which was given in the abstracts of 

 the proceedings of the Geological Society of London 

 for May last. 



The striation there referred to is found, I believe, 

 in great perfection at Holywell, a place intermediate 

 between Eastbourne and Beachy Head, confined 

 especially to the hard chalk marl used by lime- 

 burners. It first came under my notice some years 

 ago, when my impression was that it was due to 

 the rubbing of one block of the material against 

 another in the process of elevation of the mass ; 

 but further examination of the subject has led nie 

 to arrive at a diff'erent conclusion. 



In January, 1872, Dr. Ogier Ward read a paper 

 on the subject at a meeting of the Eastbourne 

 Natural History Society, in which he referred the 

 appearances to the cause above mentioned, and 

 exhibited specimens of green-sand rock somewhat 

 similarly marked, but having more the appearance 

 of true slickensides. 



It is not easy, without examining the markings 

 in situ, to obtain a clear comprehension of their 

 character, but the following description may help to 

 a conception of the appearance. 



Wherever the rock has been fissured, the walls 

 of the fissures display a sharp, straight striation, 

 consisting of narrow grooves and ridges of different 

 degrees of thickness, — an appearance such as might 

 be produced by a very fine-toothed comb being 

 drawn straight along the surface of a somewhat 

 plastic surface. The striation continues unin- 

 terruptedly, however uneven the surface may be 

 —over ridges and into hollows, and over surfaces 

 many yards in extent. 



In all cases, the direction of the striation on 

 large blocks seems to be m the direction of the dip 

 of the deposit. It is never perfectly horizontal, nor 

 perpendicular. 



Examined under the microscope, the ridges 

 present a smooth appearance, somewhat resembling 

 the surface of a stalactite, and are of a darker hue 

 than the rest of the substance. 



Wherever any lump of the marl is cracked 



N 2 



