Notes and Memoranda. 319 



Tour in Iceland in the Spring and Summer of 1862. By C. W. 

 Shepherd, M.A., F.Z.S. (Longmans.) — An elegant little book, with 

 two coloured plates of Icelandic scenery, and containing a readable 

 narrative of exploration into parts of* the island which have escaped 

 previous tourists. The picture of the hardships to be endured by 

 travellers among the hospitable, but poorly provided Icelanders, is 

 not very inviting, and agrees substantially with the experience of 

 other travellers. Scattered through the work are many interesting 

 illustrations of the physical geography of the island, and of the 

 effects of its severe winters. Of a valley near the Dranga Jokull, 

 the writer remarks, "No place could show the awful effects of the 

 breaking-up of an Icelandic winter more than the valley before us. 

 It was itself a deep ditch with mountain walls. Through the 

 centre ran several broad glacier streams, white and rapid, inter- 

 secting one another in every possible manner and direction. Huge 

 snow-drifts also climbed the mountain sides, and large masses of 

 rock and earth were strewn about, having descended from the 

 heights above. One mass in particular drew our attention. We 

 saw it long before we reached it, and thought it was a house in the 

 distance. It had bounded into the centre of the valley, and was 

 so strongly held together by the turf upon it, that it remained 

 unbroken, and presented the shape of an arch with a span of ten 

 feet, and would almost admit of my walking under it." The 

 account of an eider duck island is likewise very interesting, and the 

 book will well repay perusal. 



NOTES AND MEMORANDA. 



Devitrification" of Glass. — M. Clemandofc has a paper in Comptes Rendus 

 in which he states that desiring to make a very simple and very dispersive crown 

 glass, he used silica and soda exclusively, without any lime, and with great excess 

 of the first material. While in complete fusion at a high temperature he withdrew 

 a portion of the glass which remained unchanged for ten years, but the mass left in 

 the crucible underwent devitrification as it cooled. He adds that glass is most 

 solid and most unalterable when it contains the greatest number of bases in its 

 composition, but that an excess of any material leads to devitrification. 



Variation of Species. — M. C, Dareste brings before the French Academy an 

 instance of the progeny of a hen near Lille resembling the so-called Ponies de 

 Padoua, as Polish fowis are improperly called. Two chickens, which died before 

 they were hatched, exhibited the peculiar protrusion of the brain between the 

 frontal bones, which characterises this breed, although no trace of its having been 

 at any time crossed with the Lille fowls could be discovered. In another case a cow 

 and calf assumed the characters of a bovine race of South America, the nata, or 

 nidia, which had a peculiarly short dog-like head, and which seems to have com- 

 pletely disappeared. Several other cases are mentioned in the same paper. 



Huggins on the Spectrum of Mars.— -Mr. Huggins' paper in Monthly 

 Notices shows that the C line in the solar spectrum exists also in the spectrum of 

 Mars. A strong line distant from C, at about one fourth the distance from C to 

 13, which does not exist in the solar spectrum, was satisfactorily determined. 

 Faint lines were seen on 14th Feb., on both sides cf D, similar to those which 

 appear when the sun's light traverses the whole of the atmosphere, and which 

 were in like manner to be produced by the atmosphere of Mars. 



Mr. Browning's Sun Screen. — Mr. Browning has adopted a modification 

 of Foucault's proposal to silver an object-glass by Liebig's process, and view the 



