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HARDWICKE'S SCIENCE-GOSSIP. 



Maclaren's masterly exposition of the structure of 

 Arthur's Seat, that which requires a second period 

 of eruption upon the same site, but subsequent to 

 the deposition, the upheaval and the denudation of 

 the whole of the Carboniferous rocks, is beset with 

 the gravest difficulties. The Tertiary and Secondary 

 epochs have in turn been proposed and abandoned as 

 the period of this supposed second period of erup- 

 tion ; and it has more recently been placed, on very 

 questionable grounds, in the Permian. The antece- 

 dent improbabilities of this hypothesis of a second 

 period of eruption are so great, that it was aban. 

 doned by its author himself before his death. A 

 careful study of the whole question by the aid of the 

 light thrown upon it in comparing the structure of 

 Arthur's Seat, with that of many other volcanoes, 

 new and old, shows the hypothesis to be alike un- 

 tenable and unnecessary. The supposed proofs of a 

 second period of eruption, drawn from the position 

 of the central lava column, the nature and relations 

 of the fragmentary materials in the upper and 

 lower parts of the hill respectively, and the position 

 of certain rocks in the Lion's Haunch, all break 

 down on re-examination. While, on the other 

 hand, an examination of Arthur's Seat, in connec- 

 tion with the contemporaneous volcanic rocks of 

 Eorfar, Fife, and the Lothians, shows that in the 

 former we have the relics of a volcano which was at 

 first submarine but gradually rose above the Car- 

 boniferous sea, and was the product of a single and 

 almost continuous series of eruptions. 



NOTES AND QUERIES. 



Vibration of Gnats. — In connection with 

 Windsor Hambrough's note on the vibratory 

 motion of gnats at rest, I may mention that I have 

 often seen spiders when touched, blown upon, or 

 even only looked at, cause themselves to vibrate so 

 rapidly in the centres of their webs that, they are 

 for the time invisible, the motive evidently being a 

 desire for concealment. — W. G. Piper. 



A Novel Mousetrap.— The Sussex Daily News 

 states that at Angmering a singular and amusing 

 incident occurred at the house of one of our villagers 

 the other day. It appears that a mouse, being 

 hungry, ventured on the kitchen table. Seeing 

 some oysters with their shells apart, he made up 

 his mind to a quiet repast. He accordingly inserted 

 his head between the shells of one, but the bivalve 

 being still alive, objected to this intrusion, and 

 closed its shell; killing the mouse upon the spot. 

 Several persons were in the room at the time, and 

 can testify to the accuracy of this account. - 



Frost Phenomena. — When a sharp frost sets 

 in in the Lake district the level of the water in the 

 larger lakes quickly falls as in a dry summer. So 

 noticeable is this, that the boatmen and fishermen 

 say, " the frost nips the water off the lake." The 

 real reasons are, I believe, obvious. In frosty 

 weather the rainfall ceases, the drainage and the 

 rivulets (the feeders of the rivers) on the mountains 



are very quickly frozen up, the outflow from the 

 lake all the time going on freely unimpeded by' the 

 frost, because the volume of the stream is large, 

 and much nearer the sea-level. Although not 

 exactly bearing on the remarks by Mr. H. B. 

 Bidden, in your last, I ask an explanation of the 

 following : 1 cannot reconcile the existence (as we 

 had it on the north-west coast at the end of De- 

 cember) of a very thick fog over land and sea for 

 four or five days and nights continuously, without 

 any wind, and with the thermometer constantly 

 beiow 20°, the watery particles not freezing until 

 they touched our hair or rough coats or caps : why 

 didn't the log freeze and fall as snow ? Was motion 

 of the air required to induce crystallization ? Then 

 when that motion was artificially produced (by the 

 passage of a quick railway train or a steamboat), 

 why did not the watery particles freeze ? During 

 one of the coldest nights the water in the bottle on 

 my dressing-table was frozen solid, but the bottle 

 was not burst in the usual fashion, but the ice was 

 forced out of the neck two inches, raising the glass, 

 which was inverted over it. I imagine this was as 

 good an example of the plastic flow of ice as any 

 furnished by a glacier. The noise during the night 

 while this expansion of the contents of the bottle 

 was going on was disturbing. — Anthony W. Wilson, 

 Ulcerslon. 



Do Fishes tjtter Sounds?— Tn catching weak 

 fish in the inlets on the Atlantic coast of New 

 Jersey, I have often noticed the phenomenon to 

 which your querist alludes. The sound certainly 

 proceeded from the ; tish, though, as 1 venture to 

 conclude, the acion which caused it was not in- 

 tended to produce it ; had the fish been in water, 

 probably there would have been no such motions, 

 or the motions would not have produced the sound. 

 —J. Burkitt Webb, C.E., Illinois, U.S. 



Musselling. — I should feel much obliged if 

 some of your numerous correspondents would throw 

 some light on the cause of the complaint popularly 

 called " musselling." Is it caused by any other 

 kind of shell-fish besides mussels ? I have seen it 

 referred to the presence of the pea-crab, to the 

 byssus, or " moss," as well as to the decomposed 

 state of the mollusc. This question is of so much 

 importance, both scientifically and economically, 

 that I should be glad to see it as well discussed in 

 the pages of Science-Gossip as many other subjects 

 have lately been. — C. B. 



Geranium molle. — There grows on a particular 

 hedge-bank near my residence, a perfectly white 

 variety of, 1 believe, G. molle, though it seems to 

 have a stronger musky scent than that, species. As 

 several botanical friends to whom shown are unac- 

 quainted wiih it, 1 should like to know if any of 

 the readers of Science-Gossip have met with it 

 elsewhere.— W. llenidge, Wincunton. 



Marine Aquaria. — Some years ago, after many 

 failures, I succeeded in keeping a small marine aqua- 

 rium in perfect order for a long period, and the result 

 of my experience may be of use to some of the readers 

 of Sqiexce-Gossip. Any kind of sand is suitable for 

 the bottom, if washed perfectly clean. I tried a 

 variety of the larger algae, such as are usually put 

 in aquariums, but found none of them quite satis- 

 factory. Ultimately 1 entirely depended for a 

 supply of oxygen to the inhabitants of my aquarium 

 on the minute green alga; that are sure to come 

 sooner or later in all aquaria, and cover the pieces 

 of rock, &c, like green velvet. I differ from your 



