100] 



HARDWICKE'S SCIENCE-GOSSIP. 



Both are found in the same locality— viz. the Cam- 

 brian rocks of Bray Head, about four or five miles 

 from Dublin. The place is easily reached, and will 

 not soon be forgotten by the geological student. 

 The rocks where the Oldhamia occur are beyond 

 the village, and form the southern horn of the bay. 

 They are very smooth and fissile, and almost of a 

 claret-colour. The fossils (which sometimes occur 

 along with the traces of marine worms) seem to 

 lie in zones, for certain strata yield them more 



! easily spend a few days here. Nor would his plea- 

 sure be marred by the demonstrative gaiety of the 

 humble wedding-parties that seem to make Bray 

 their place ot festivity. The village is easily reached 

 by rail from Dublin, and we regard it as especially 

 interesting to the geologist as the locality where 

 the "oldest British fossil " may be met with. 



Fig. 61. Oldhamia antiqua, the oldest known British fossil : 

 Cambrian Rocks, Bray Head, Ireland. 



abundantly than others. In the neighbourhood of 

 the bathing-place, where the sea-water appears 

 unusually pure and green in comparison with the 

 claret hue of the rocks, the Oldhamia may be 

 gathered in abundance. The species antiqua also 

 occurs in yellowish shales of the same geological age, 

 in Carrick mountain, county Wexford. Hitherto, 

 both species have been limited to the Cambrian 

 rocks of Ireland, where, however, they do not seem 

 to have a very wide distribution. The other species 

 {Oldhamia radiata) differs from that figured in 

 having the setai circularly radiated instead of being 

 fan- shaped. It is also found at Bray Point, county 

 Wicklow, and the student will readily meet with it 

 there, in the rocks known to all in the neighbour- 

 hood as the " Periwinkle Bocks." 



Apart from the pleasure of collecting these neat 

 little fossils, the visit to Bray Head will amply 

 repay the tourist. It is one of the pieasantest sea- 

 side watering-places in Ireland. The zoology of 

 the rock-pools about the Head is very rich, and the 

 visitor interested in this study and geology might 



ON COBWEB-MAKING. 



SOME observations made upon the house spider 

 {Tegenaria domestica), have thrown light 

 sufficient to satisfy my own curiosity with regard to 

 the power which all spiders have of ejecting lines 

 of web to a distance. The usual explanation of the 

 manner in which a garden spider will send lines 

 from one object to another, is, that the line is first 

 ejected from the spinnerets, and, floating on the air, 

 is caught by some object at a distance, when the 

 spider avails himself of it as a bridge, strengthening 

 it as he goes along. 



As webs are generally formed by the garden 

 spider in the very early morning, or after dark at 

 night, it is exceedingly difficult to watch the process 

 from the first of constructing webs of Epeira 

 diadema, the garden spider; but from observing 

 the powers of the house spider I am of opinion that 

 all spiders are able to eject and attach lines of web 

 just where they wish, and that there is nothing 

 fortuitous about the process. My conclusions are 

 drawn from the following facts : — 



I obtained last year, in the month of February, a 

 cocoon, half full of house spiders ; one end of the soft 

 silken ball appearing quite black with the number 

 of busy spiders huddled together, while the other 

 half was filled with the empty shells of the eggs 

 from which they had emerged. With the point of 

 a needle 1 made an aperture in the cocoon, and let 

 about ten of the creatures free, being anxious to see 

 whether they would exercise their web-spinning 

 power soon after their entrance upon life. It so 

 happened that I allowed them to escape on to a book 

 with a cover which I had laid across the end of a 

 marble mantelpiece ; the spiders immediately ran 

 about, and several let themselves down by lines a 

 few inches from where the edge of the book pro- 

 jected beyond the mantelpiece, as if to reconnoitre, 

 but quickly returned again. Suddenly I perceived 

 that from one of the small creatures, after being for 

 a time motionless, a line of web of exquisite fineness 

 had been put up, at about an angle of 45°, to the 

 edge of a terra-cotta vase which stood on the other 

 side of the book, and was about ten inches high. The 

 line was taut, and firmly fixed, although so fine. 

 No portion of it hung over the edges of the vase, 

 which was not rounded, but angular, and about a 

 fourth of an inch wide, and the web had exactly 



