HARDWICKE'S SCIENCE-GOSSIP. 



101 



become horizontal ; at Llanishen the dip is about 22 

 degrees to the S.W., gradually increasing in angle of 

 dip as the tunnel is approached, where the beds are 

 seen to fold over an anticlinal axis and again dip to 

 the N.E. at an angle of 33 degrees. 



A trip by the steam ferry, occupying about ten 

 minutes, lands you at Penarth, where one of the best 

 sections of the Rhastic series in this country is exposed 

 in the cliff. Penarth Head, about 160 feet high, con- 

 tains the following series of beds. The base consists of 

 red and pale green marls, enclosing large lenticular 

 masses of gypsum. Beds of impure limestone succeed — 

 the surface of one of these beds presents a very uneven 



ing the site of the coast line of the Triassic Sea, it 

 consists of angular, subangular, and water-worn blocks 

 of the older rocks of the districts cemented in a 

 matrix of a rich red colour ; the stone can be wrought 

 in blocks of almost any dimensions, and is much used 

 when substantial masonry is required. Hitherto it 

 has not furnished the writer with any fossils other 

 than those found in the contained blocks of older 

 rocks. 



The amount of denudation which has taken place 

 in this district is enormous. Abundant evidence re- 

 mains to convince any one the coal strata must have 

 been continuous from South Wales to the Bristol and 



Fig. 90.— Section from Cardiff to Caerphilly. 1. Coal measures; 2. Millstone grit; 3. Carboniferous limestone; 4. Old Red 



Sandstone; 5. Silurian; 6. Gravels; 7. Trias. 



surface when exposed, in the depressions of which 

 large quantities of fish remains occur, consisting of 

 teeth, spines, and scales of various species, prominently 

 among which may be mentioned Nemaca?ithus filifer, 

 N. monilifer, Hybodus retiadatus,' Acrodus minimus, 

 Sargodon Tomicus, Gyrolepis Alberti, Saurichthys 

 apicalis, and S. acuminatus. Then follow a series of 

 black shales, with occasional beds of impure lime- 

 stone but exceedingly fossiliferous, containing Axinus, 

 Pullastra, Pecten Valoniensis, Cardium Rhaticum, 

 Avicula contorta, Myophoria postera, Gervillia, 

 &c. These beds are succeeded by the White 

 Lias series, commencing with sandy shales, passing 

 into beds of limestone containing Lima precursor, 

 Modiola minima, Anatina Suessi, and still ascend- 

 ing we met with the Ostrea beds containing Ostrea 

 liassica, Plicatida, Lima shales, with Lima precursor, 

 and lastly the Ammonites Planorbis beds with the 

 fossil giving them their title. Reptilian bones are 

 not unfrequently met with, consisting of Ichthyosaurus, 

 Plesiosaurus, &c. 



Following the cliff along to Lavernock, about two 

 miles in a southwardly direction, the various beds 

 may be examined in detail, as their undulations bring 

 them within easy reach for observing more minutely. 



At Lavernock the coast suddenly trends to the west 

 and a very fine exposure of the Lias opens up. The 

 beach from low water to the base of the cliff is covered 

 with some of the beds, the natural fracture of which 

 gives the beach the appearance of having been 

 artificially paved. From this point the flat and steep 

 Holmes (two islands of carboniferous limestone) are 

 prominent objects standing off in the channel about 

 three or four miles from the mainland. 



At Radyr and at the junction of the Penarth line 

 with the Taff Vale Railway near Llandaff, excellent 

 exposures of the dolomitic conglomerate occur, mark- 



Somerset coal-field, as also the underlying Old Red 

 Sandstone. The vertical thickness of these rocks 

 added to those exposed in the cliffs from Penarth to 

 Southern- down amounts to between one and two 

 miles, a mass of rock which only a corresponding 

 immensity of time would be sufficient to remove. 



W. H. Harris. 



THE PREPARATION OF INSECTS FOR 

 MICROSCOPICAL EXAMINATION. 



By H. M. J. Underhill. 



THERE is a great deal of literature on the subject 

 of " microscopical mounting," and I hesitated 

 much before I decided to contribute yet another 

 paper to the amount Notwithstanding, I believe 

 that the particular branch of "mounting " of which 

 this article treats, is but imperfectly understood. 

 When I was a member of the Postal Microscopical 

 Society, I used to see the slides of some hundred 

 and twenty microscopists, among which were a great 

 many of what the club calls "professional slides." 

 It seemed to me that the majority of the entomological 

 specimens, both those by "amateurs" and "pro- 

 fessionals " were badly set up, and that, with a few 

 agreeable exceptions, even those which might be 

 called good slides were mounted upon principles 

 radically faulty. This being a fairly large circle 

 from which to judge, I suppose that most entomo- 

 logists who use a microscope set up their preparations 

 after the same fashion, and therefore I have written a 

 paper on a well-worn theme. 



A man commencing the study of insect-anatomy 

 reads a few " hints on mounting " in some book ; the 



