HARDWICKE'S SCIENCE-GOSSIP. 



75 



grey in stripes, are too conspicuous to permit his 

 being easily forgotten when once seen. He stalks his 

 prey, which consists of small flies, very small ones, 

 for he is not much over a quarter of an inch in length 

 himself. I have called him clever ; and so he is, as 

 far as the stalking goes. Yet I once saw one of these 

 little creatures most awfully taken in, in the exercise 

 of this power which they possess of stalking their prey. 

 It was on a rather rough stone wall in Warwickshire, 

 last year ; the Saltici were hunting about in all direc- 

 tions for game, which was plentiful enough. On the 

 wall some one had squashed a fly, so that the wings 

 and the empty chitinous membranes which enclose 

 and protect the legs and thorax, remained sticking to 

 the wall by means of the dried contents of the body. 

 Presently the wing, or some other portion of these 

 melancholy remains, caught one or more of the eight 

 eyes of our friend the Salticus, and he immediately 

 made up his mind to dine off it. So he began with 

 extreme caution to stalk the supposed fly, creeping, 

 with his legs bent to their utmost extent, from point 

 to point of the stone. Taking advantage of every 

 little roughness and prominence, he at last arrived 

 quite close and then sprang like a tiger (at least as I 

 suppose a tiger would spring, and I am glad to say 

 I have not seen it done), upon his prey. He took 

 his disappointment very philosophically and went off 

 in search of better luck at once. This I take to be 

 another proof of the short-sightedness of spiders. 



The last example of this highly interesting group of 

 invertebrates is our large and common garden-spider 

 (Epeira diadema), the white cross on whose yellow 

 back is familiar to nearly every one. Epeira diadema 

 is one of our largest spiders, and also one of the 

 handsomest inhabiting this island ; it belongs, more- 

 over, to a large genus and one which has been 

 remarkable for ages for the beauty and ingenuity of 

 their webs. Diadema is found commonly enough on 

 furze-covered commons and in gardens and lanes, in 

 fact nearly everywhere, during the autumn months. 

 This spider spins the well-known polygonal web, 

 with its transverse spinal thread, which everyone 

 knows, and which can be told from that of smaller 

 members of the same genus from the size of the 

 meshes. It has a curious habit of shaking its web 

 violently ; and so rapid are its oscillations in this 

 act, that the spider cannot be seen at all ; whether 

 this is to clean the web from adhering particles or 

 whether it is for concealment, I do not know. But I 

 scarcely think the former, because the same move- 

 ment which shook off the adhering particles would 

 surely scatter the little glutinous globules, with which 

 the threads are studded, and which hold the prey ; 

 neither do I think the latter is the probable cause, for 

 on alarm being taken, the spider immediately drops 

 to the ground by a thread. This spider has a habit 

 with all its larger victims, of surrounding them with a 

 shroud of silk, by spinning them round and round, 

 before beginning to feed on them. In fact I have 



seen wasps so completely shrouded in this way that 

 they were perfectly helpless. This spider either lies 

 in wait head downwards in the centre of its web, or 

 else lies concealed close at hand with its front pair of 

 legs on one of the main supporting threads of the 

 web, so that the least movement in it is communicated 

 to its guardian. 



I could write much more on this interesting and 

 almost inexhaustible topic, but I am afraid of taking 

 up too much space, and moreover of tiring your 

 patience. 



SOMERSETSHIRE SAND-TOTS :— THEIR 

 GEOLOGICAL HISTORY. 



THE geological history of blown sand is one of 

 much interest. It plays an important part in 

 the present phase of earth history, and opens up a 

 variety of interesting avenues of fact and speculation 

 in connection with the past history of the crust of our 

 globe. Sand differs a good deal in quality and com- 

 position, being locally more or less abraded, and 

 more or less mixed with organically derived and 

 other matter, but in the main consists of quartz. It 

 is coarse or fine generally according as it has travelled 

 a short or long distance ; for sand is a considerable 

 traveller, and its origin has to be looked for often at 

 great distances from where we find it. Wherever we 

 find it, it has travelled ; whether in the quiet bays of 

 mountain brooks or on stretches of sea-shore, it has 

 generally proceeded a greater or less distance from 

 the rocks which produced it. How, then, is it pro- 

 duced ? By water eroding the rocks in which it was 

 originally more or less massive, and by the subsequent 

 wear and tear of friction in water-channels. How it 

 accumulates is at first sight not quite so obvious ; but 

 the process is nearly the same whether the accumula- 

 tion be small or great. It is in the main a process 

 of sifting ; and the sifting is done by water-currents. 

 Wherever rills trickle into streams, streams into 

 rivers, and rivers into the ocean, the currents are 

 constantly carrying off the finer and softer particles 

 first, and redepositing these as muds or clays in quiet 

 waters ; leaving behind at first the larger fragments, 

 whether soft or hard, until trituration has reduced 

 the softer of these to fine particles. These again are 

 removed and the harder parts are left behind in the 

 form of sand, gravels and pebbles, to be again 

 abraded and again carried down. This process has 

 been ever going on, and we find sand in one form or 

 other, in tremendous accumulations as rock, or sand- 

 stone in every known formation, and in some forma- 

 tions to the comparative exclusion of mud-rocks or 

 shales. The estuary of the Severn illustrates the 

 formation of sand in a very good way. The strong 

 tidal currents sift the eroded and triturating material 

 continually. New sand-banks form, the channels 

 alter and immense quantities are carried down and 

 deposited in the sea. 



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