240 Scientific Intelligence. 



rent. Nearly all these conclusions are based upon results repre- 

 sented by average numbers obtained by series of experiments.— 

 Proc. Boy. Soc, No. 236. 



2. Electrical Resistance of the new alloy Platinoid. — The new 

 alloy Platinoid is essentially German silver with the addition of 

 1 or 2 per cent of metallic tungsten. It has a specific gravity of 

 8-18 (at 20° C.) ; the color is white, and when polished is hardly 

 distinguishable in appearance from silver ; it is especially remark- 

 able for being practically untarnishable, resisting to great degree 

 the ordinary tarnishing effect of the air. Bottomlet has carried 

 on a series of experiments having as their object the determina- 

 tion of its electrical resistance. He finds that it possesses the 

 same properties of high specific resistance and small variation of 

 resistance with change of temperature that make German silver 

 wire so suitable for the galvanometer and resistance coils, only in 

 a higher degree. The specific resistance of platinoid is about one 

 and a half times that of German silver. The average percentage 

 variation of resistance per 1° C. between 0° and 100° was found to 

 be - 0208'7 in one case and 0*022 in another ; the corresponding 

 values, as obtained by Matthiessen are at 20°, for copper 0*388, 

 platinum-silver alloy 0*031, gold-silver alloy 0*065 and German 

 silver 0'044. — Proc. Boy. Soc, No. 237. 



3. Annual change of the Aurora Borealis. — A recent number 

 of Nature contains an interesting review of a work by Tromholt 

 on the Aurora. After remarking the fact that Weyprecht was 

 the first to advance the view that the auroral zone is farthest 

 south at the equinoxes and farthest north at the solstices, the 

 following quotation in regard to this point is given from Trom- 

 holt. 



" My researches have led me to endorse Weyprecht's theory. 

 I feel satisfied that the Aurora Borealis moves toward the 

 autumnal equinox southward, and then northward, reaching its 

 farthest northern limit about solstice. After this it again moves 

 southward, being in its most southern position at the vernal 

 equinox, when the movement is again in a northerly direction. . 



" From this it follows that the two maxima occurring in the 

 temperate zone at the equinoxes must approach each other more 

 the farther north the point of observation is situated. This is, in 

 fact, the case. As some examples, I may mention that, while the 

 two maxima occur in March and September in St. Petersburg, 

 Abo, Stockholm, Christiania, Worcester (Mass.), and New Haven, 

 they occur in February and October in Aalesund, Newberry, 

 Quebec, and Newfoundland ; in December to January in Ham- 

 merfest, and in January at Fort Reliance. Very instructive in 

 this respect are also the observations from the three Greenland 

 stations : Upernivik, Jacobshavn, and Ivigtut. At Ivigtut, the 

 southernmost of the stations, the yearly maximum must certainly 

 be said to occur in January, but there is a second maximum toward 

 the autumnal equinox. At Jacobshavn, eight degrees farther north, 

 there is but one distinctly marked maximum in January, and at 



