130 



SCIENCE- GOSSIP. 



loose slopes of the Glycler Fawr, finally breaks 

 away in the precipices overlooking Llyn Idwal. 

 Among the mixed assemblage of rocks in this 

 neighbourhood are some particularly fine examples 

 of ripple-marked flags, while the surrounding 

 rocks are mainly felspathic conglomerates, often 

 scoriaceous andbrecciated. Eastward the toilsome 



since swept down every valley and held in silence 

 the hillside, now so noisy for neaidy all the year 

 with running streams. The Alpine plants that 

 later were wide-spreading are now confined to the 

 higher slopes. 



The destructive agents of denudation slowly yet 

 persistently carry on their work, and doubtless in 



From PhoU] 



Ripple-marked Rocks above Llyn Idwal. 



[by A. W. Dennis. 



slope of the Glyders is crowned by huge boulders, 

 piled in the most remarkable confusion, succeeded 

 lower down by sharp screes and the weathered 

 outcrop of the slaty beds that underlie in a 

 synclinal curve the felspathic ash of the upland 

 valley. Further to the north a scene suddenly 

 comes into view unequalled for its severity even 

 in North Wales. The mountain sweeps down in 

 sheer cliffs and boulder-strewn slopes to Llyn 

 Idwal, 800 feet below. Beyond, the Nant Francon 

 Pass stretches northward, its rocks showing signs 

 of moving ice, nearly as pronounced as in the 

 Llanberis Pass. Immediately below are the moraines 

 now so well known by most tourists, who are 

 attracted to this much-visited spot by the great 

 cleft in the rocks known as the Devil's Kitchen. 

 Seen from above, the moraines appear to be arranged 

 in three lines of mounds, indicating three periods 

 in the retreat of the glacier during the slow im- 

 provement of the climate. 



Such is a rough outline of some of the most con- 

 spicuous records left by the long-vanished ice. 

 Standing on these hills, it needs but little 

 imagination to picture the ice sheets which ages 



time will reduce these at present prominent records 

 to geological features, as difficult to identify as 

 are those supposed glacial deposits associated with 

 earlier geological periods. 



122 StoeJmell Park Road, Brixton. 



Eemarkable Hailstones. — During a severe 

 thunderstorm in this district on August 10th last, 

 amongst the hailstones which descended one was 

 of an unusual size, as seen in this country, being 

 as large as a good-sized marble, and split exactly 

 in two. On observing the two halves I found it 

 was of perfectly transparent ice ; one section con- 

 tained several small white rings, growing less as 

 the nucleus was reached, similar to the laminations 

 of an onion. I am not aware that the mode of 

 formation of hailstones has ever been satisfactorily 

 explained ; yet the large globules of ice above 

 described seem in some way to connect it with the 

 electrical state of the atmosphere. According to 

 the sectional view, it appears to me that its great 

 size is accounted for by supposing it to bean aggre- 

 gation of smaller ones. Raindrops and snowflakcs 

 increase in size as they approach the earth, so may 

 hailstones aggregate together in their downward 

 fall, becoming larger and larger. The air was mild at 

 the time of the hailstorm, which occurred at 7 a.m. — 

 J. C. Mills, Plas-Belyg, Llanrmst, Korih Wales. 



