HARDWICEE'S SCIENCE-GOSSIP. 



35 



displaying it ; but in general he carries it as a flat, 

 broad pencil. When spread, the fan is made up of 

 small bundles of the peculiar tail-hairs, with a long 

 feather or two in their intervals. 



Let us examine these hairs under a power of 

 about two hundred diameters. They are nearly 

 one-fourth the length of the whole body (which 

 whole length, by the way, may be called a line or a 

 line and a half), and are prettily ornamented with 

 small and nearly opposite branches placed in pairs 

 along their stems, and lying close to them, to the 

 number of twelve or fourteen. But the crown, or 

 top of the hair, is its principal beauty. It is grace- 

 fully bent over, like the head of a bell-flower, and 

 forms three, or sometimes four, pendants, slightly 

 clubbed at their extremities, the one nearest to the 

 stem extending lowest down it, and the outermost 

 finishing in a spur directed upwards. When the 

 tail is expanded, these pretty heads are somehow 



Fig. 18. P. Lagurus. Hairs of Tail, x 200. 



locked together in groups, so as to form conical 

 apices to the bundles which I have before de- 

 scribed, while the tiny branches of the stems give 

 to the whole a beautiful dotted appearance, well 

 seen with reflected light. A small group of the 

 "feathers" proceeds from the extremity of the 

 body, gracefully dividing the fan into two parts. 

 We will now examine the feathers of the tufts. 

 They are continued, as I have said, across the back 

 in double rows, and their quill ends, if I may so de- 

 scribe them, are hooked, apparently to afford lever- 

 age for their elevation or depression ; for I have 

 sometimes seen the little creatures walking about 

 with the front of each pair of rows elevated, and the 

 hind one flat upon the back ; and when at the same 

 time the tail was expanded, the effect was very 

 pretty, and I have almost thought that " as proud 

 as Polyxenes " might be substituted for " as proud 

 as a peacock," thereby relieving the glorious bird 

 from the monopoly of pride which has been forced 

 upon him. The limb of the feather, which is of a 

 rich brown colour, is club-shaped, being thicker 

 at the extremity than near the quill, and slightly 

 curved. It is four-sided ; that is to say, if it were 



possible to cut one transversely, the section would 

 appear as a cross, and each of the four borders is 

 deeply serrated. A fringe of these feathers sur- 

 rounds the anterior part of the body and head, but 

 in these positions they are not arranged in tufts. 



There is much more to be said about our little 

 myriapod, — of his several simple eyes,* his stout 

 seven-jointed feelers, of his mouth, his gizzard lined 

 with teeth, and of his skin, so beautifully marked 

 and pitted for the attachment of the tail-hairs ; but 

 my aim is rather to whet the appetite of some 

 young microscopist than to satisfy it. There is 

 plenty more for him to examine before the interest 

 of our subject is exhausted ; and having well enter- 

 tained himself with this "entertainer of many 

 friends," I would say to him, in the words of the 

 other Polyxenes, i.e. Shakespeare's : 



" I beseecli you, 

 If you know aiight wiiich does behove my knowledge 

 Thereof to be informed, imprison it not 

 In ignorant concealment." 



Diss, Norfolk, November, 1871. 



T. A. 



A RIVER- VALLEY AND ITS TRIBUTARIES. 



THE excavation of a river-valley, including all 

 its branches and minor feeders, is a problem 

 still to be satisfactorily solved, although the new 

 school of subaerialists would persuade us they 

 understand all about it. They state "that for 

 one valley which happens to run a long the line of 

 a dislocation there are fifty or a hundred which do 

 not ;" and an ardent Scotch advocate of the theory 

 even goes so far as to assert "there is no point 

 which the detailed investigations of the geological 

 survey have made clearer than this." I, however, 

 during about twenty years of work in the field, have 

 found that valleys in connection with which there 

 could not be a break are, comparatively speaking, 

 rare, while those having their associated disloca- 

 tions are numerous ; and of the rest, few, probably, if 

 their structure was visible, would be unconnected 

 with cracks or dislocations of the underlying rocks. 



The rocks at the downthrow side of a fault seem 

 nearly always to be more susceptible of denudation 

 than the rocks at the other side; consequently, as a 

 valley forms, it is inclined to gradually extend away 

 from the original line, which would lead a theorist 

 or hasty observer to suppose no connection between 

 the two to exist. 



The favourite example of the subaeriahsts to prove 

 their theory is a flat shore, from which the tide is 

 retreating, and on which minute river-systems form. 

 This, however, is not a true representation of the 

 earth's surface, as it is more or less wet ; but if an 

 observer will visit the strand on a warm day.hewill 



• Tliese eyes are easUy seen in living specimens, but 

 difficult to make out in dead ones. 



