532 



NA TURE 



[September 27, 1900 



magnetic observatory is now being erected sixteen miles to the 

 south-east of Washington City, and a fourth observatory is, 

 temporarily, in operation at Baldwin, Kansas. The last named 

 observatory is central to the area being surveyed by four mag- 

 netic parties, and it will be shifted about in the western States 

 according to the requirements of the magnetic survey. . It is 

 the intention to have the four observatories ready in time to 

 co-operate with the Antarctic expeditions. 



In connection with the usurpation of swallows' nests by house 

 Sparrows, Mr. J. H. Allchin sends a description of a swallow- 

 cumsparrow's nest seen by him at Dymchurch, in the Romney 

 Marsh. The original nest was built on a beam immediately 

 under the corrugated iron roof of a shed, but the usurpers had 

 so completely covered it with straw, grass, feathers, fibres and 

 other materials, that it was almost impossible to see any portion 

 of it. Mr. Allchin remarks : "I have seen other nests of 

 swallows which had been taken possession of by sparrows, but 

 in those instances the only evidences of occupation were bits of 

 straw or grass sticking out of the entrance ; this is the first one 

 I have seen covered over so thoroughly as to completely hide 

 he work of the original builders. 



. Another successful experiment with electric traction on 

 railways is reported from Germany, the line being from Berlin 

 to Zehlendorf on the new Wannsee railway. The train in 

 question (says Feilden^s Magazine for September) was equipped 

 as if actually running to scheduled time. It was furnished with 

 a motor car at each end, the work of propulsion being divided 

 equally between them, the advantage claimed for this being 

 that the reversing of the train becomes unnecessary at the end 

 of each journey. Eight ordinary cars were employed in 

 addition, seating in all 400 passengers. These experiments are 

 to be continued over a period of one year, at the termination of 

 which it is expected that the question will be decided whether 

 or not electric propulsion is to be wholly substituted for steam 

 power, while at the fsame time much useful data will be 

 gathered. An advantage already claimed is that electric 

 motive power is about 15 per cent, cheaper than steam, and 

 also at higher velocities the chance of accidents is supposed to 

 be less. A train of this description is at present on trial in this 

 country, and it will be useful to compare notes from each when 

 the material is available. 



From all quarters we learn that the present season has been 

 remarkable for the appearance of numerous specimens of the 

 clouded yellow butterflies (Colias edusa and C. hyale), as well 

 as the holly-blue [Lycaena argiohis). During one country walk 

 of three miles in Cambridgeshire, on August 13, the present 

 writer saw three hyale and one edusa ; in a garden near Brighton 

 a holly-blue was seen on September 4, and many collectors 

 report having obtained fair series of one or both of the two 

 yellows in a day's hunting. From Science Gossip we learn that 

 the variety helice of C. edusa has occurred in some numbers in 

 clover fields in east Essex. The year 1892 will be remembered 

 as the last occasion on which C. edusa occurred in abundance, 

 but the present season is characterised by the comparative 

 frequency of the pale species hyale, which was far less plentiful 

 in 1892. The humming-bird moth {Macroglossa stellatarum) 

 appears to have been gaining rather more than the usual 

 notoriety in the daily papers which it has received ever since, 

 some thirty years ago, the late Rev. J. G. Wood, in his 

 "Common British Moths," wrote: "This moth, which is 

 tolerably common, has been very familiar to the public of late 

 years on account of the many letters which have appeared in 

 the daily journals, much to the amusement of practical entomo- 

 logists, who have been too familiar with the insect in question 

 to think it worth a special notice." 

 NO. 1613, VOL. 62] 



Dr. Antonio Porta communicates to the Rendiconti del R. 

 Istituto Z^W(^ar,fi7 certain studies on the anatomy of the common 

 frog-hopper {Aphrophora spuuiaria, L.) having especial refer- 

 ence to the secretion of froth, so well known to all gardeners. 

 The author finds that the apparatus which secretes the frothy 

 liquid in A. spiimaria, and possibly in other species, consists 

 of hypodermal glands scattered over the back and especially 

 near the stigma, that the corpus ovilis is perhaps in relation 

 with the secretion of froth, that the mass of cells found in the 

 latero-ventral position collect and perhaps produce material of 

 which the animal makes use in the elaboration of the secretions, 

 and that the glandular epithelium of the seventh and eighth 

 segments serve as supports for minute appendages of a branchial 

 character, which have disappeared in Cicadx and Nepa, thus 

 confirming the hypothesis of Wheeler. 



In view of our knowledge of the influence of radiant energy 

 on electrically charged bodies, much interest attaches to the 

 question whether a solar eclipse has any marked eff'ect on 

 atmospheric electricity. Dr. Julius Elster made observations 

 during the last total eclipse at Algiers, and remarked an im- 

 portant fall of the potential of atmospheric electricity at and 

 slightly after the totality. The observations are given in the 

 last number of the Memoirs of the Societa degli Spettroscopisti 

 Italian!. On the other hand, Dr. Emilio Oddone describes, in 

 the Reudiconti del R. Istitttto Loinbardo, observations made with 

 an electrometer at Pavia, where during the last eclipse eight- 

 tenths of the solar diameter were obscured. The results were 

 of a negative character. Before the eclipse, high negative 

 potentials were observed, which were attributable to clouds 

 accompanying a distant thunderstorm ; but during the eclipse 

 the variations in the electrostatic potential seem to have been 

 similar to the ordinary diurnal variations. It thus appears that 

 the eclipse exercised no very marked influence on the electric 

 state of the air ; but whether any portion of the observed varia- 

 tions was attributable to this cause is a question which it would 

 be difiicult to answer. 



Mr. David Robertson has communicated to the Proceedings 

 of the Philosophical'Society of Glasgow a short note on the 

 equilibrium of a column of air and the atmospheric temperature 

 gradient, in which the adiabatic formula for the maximum 

 gradient consistent with stability is established in a simple 

 manner. 



Parts 10 to 12 of the Meddelanden fran Lunds Astronomiska 

 Observatoriuvi contain several papers on mathematical astro- 

 nomy. One, by T. Broden, deals with some probability 

 considerations relating to the convergence of certain continued 

 fractions, a problem treated by Gyelden in 1898. Certain 

 librations in the planetary system are the subject of a paper by 

 C. V. L. Charlier, while G. Noren and J. A. Wallberg contri- 

 bute lengthy formulae for the development of the disturbing 

 function in its canonical elements. 



No. 1 10 of Ostwald's " Klassiker der exacten Wissenschaften " 

 (Leipzig, Wilhelm Engelmann, 1900) is a reprint of J. H. van't 

 Hoff"'s papers on the laws of chemical equilibrium. The three 

 papers in question are those communicated in French to the 

 Swedish Academy of Sciences about the year 1885, and deal 

 with the laws of chemical equilibrium in attenuated systems, a 

 general property of attenuated media, and the electric conditions 

 of chemical equilibrium. The present book is a translation of these 

 papers by Georg Bredig, and an appendix of twenty pages con- 

 tains a brief biographical notice of van't Hoff" and numerous 

 notes, both historic and explanatory. 



In the course of a paper on the various forms of phosphor- 

 escence, in the Revue Scientifique for September 8, M. Gustave 

 Le Bon describes a dark lamp ("lampe noire ") for the produc- 



