Feb. 28, 1884] 



NA TURE 



409 



eluding the Azorts, Madeira, Canaries, and Cape de 

 V»rde Islands) ; (2) Oriental, or, rather, Central and 

 Oriental African ; (3) Western African (from the Gam- 

 bia to the Congo); {^Soi/titern (included by a line drawn 

 from Kalabini to Limpopo, and comprising a portion of 

 the eastern coast to the Mozambique); (5) Alalagasic 

 (i.e. the Lemur country with Madagascar). Various ex- 

 peditions and other means by which materials have been 

 obtained are mentioned, and a bibliographical list is 

 given, in the introduction, of the numerous published 

 works and papers on African Arachnida from the days of 

 Linna:u3 to the present time. The .Arachnida described 

 and recorded in this first part are from Tunis, while the 

 second part (published loc. ^it. vol. .\vi. iSSi) simply con- 

 tains an account of a collection of Arachnids from 

 Inhanibane (in the southern region), with some consider- 

 ations on the .Arachno-fauna of the Mozambique, of which 

 a list of species is also added. 



The Tunisian collection described in Part I. numbers 

 115 species of six orders : Scorpionidea, 6 species (Scor- 

 piones, 5 ; Pseudoscorpiones, l) ; Solpugidea (.Solifugas), 

 4 ; P/ialangiidea (Opiliones), 4 ; Araneidca (Aranea?), 

 96 ; Acaridea (.\cari), 5. Of the above, two new genera, 

 and eleven new species (all but one of the latter — a 

 pseudo scorpion of a new genus) belong to the Araneidea. 

 As might be supposed, the essential character of the 

 Tunisian collection is South European or Mediterranean. 

 Very different from these are the arachnids described 

 and recorded in Part II. from Inhambane and the 

 Mozambique. Here we have, though the number of 

 species is very scanty, the true tropical character. Only 

 54 species are recorded, comprised in 43 genera, 20 

 families, and 5 orders. The larger part (35 species) be- 

 long to the Araneidea, of which I genus and 4 species 

 are new. Coming now to the .Arachnida recorded and 

 described in Part III. from Scioa (in the eastern zoologi- 

 cal province) we have 71 species belonging to 49 genera, 

 18 families, and 4 orders. .A general catalogue is also 

 added of Abyssinian Arachnida, which, including those 

 from Scioa, number 124 species. It is noted as remark- 

 able that no scorpions were contained in the collection 

 from Scioa, and tliat 30 of the .Arachnids recorded are 

 new to science ; also that only 12 of the Scioan species 

 are common to the rest of .Abyssinia. 



The author enters into so lie other considerations on 

 the distribution of the .Arachnids of -Abyssinia ; but the 

 researches and materials on which his observations are 

 based appear as yet to be too scanty to sustain any very 

 general conclusions. At the same time it must be 

 acknowledged t'.iat the plan on which the author has 

 worked, of bringing the materials of so large and varied 

 a region as the .African peninsula under the geographical 

 divisions announced in the introduction to Part I. is a 

 most useful one, and the work he has done so far is 

 undoubtedly a valuable contribution to arachnological 

 science. O. P. C. 



MR. BURNHAM'S DOUBLE-STAR MEASURES 

 "y HE recently published volume of the Memoirs of the 

 -*■ Royal Astronomical Society contains a further 

 series of measures of double stars by Mr. S. \V. 

 Burnham, made with the iSinch refractor of the Obser- 

 vatory at Chicago. This series comprises measures of 

 151 double stars discovered by this eminent observer, 

 which brings up the number of such objects discovered 

 by him during the last ten years to no fewer than 1013, 

 amongst which ire included some of the most interesting 

 stars of this class ; also measures of a selected list of 

 double stars, 770 in number, made chiefly in the years 

 1879 and 18S0, with an appendix, the results of observa- 

 tions of several objects, as late as the middle of the past 

 year. Every one who is interest d in this branch of 

 astronomical scien;e will read with mu;h regret one 



remark in Mr. Burnham's introduction : he writes : — 

 " The present catalogue will conclude my astronomical 

 work^ at least so far as any regular or systematic observa- 

 tions are concerned." He expresses himself modestly 

 respecting his own labours — " In a field so infinitely 

 large, one can accomplish but little at the most, and how 

 much, or how little, the astronomers of a few centuries 

 hence can perhaps best decide. ... At this time I may 

 venture to claim that my work in this field has been 

 prosecuted with some enthusiasm, and for its own sake 

 only, and that my interest has not been divided among 

 several specialities." 



But a higher estimate of Mr. Burnham's work in this 

 particular line of observational astronomy to which he 

 has devoted himself may be justly taken. To read of 

 the discovery of upwards of a thousand double stars 

 within a limited period by one observer, we might almost 

 suppose we were living in the days of Sir William 

 Herschel, when the heavens were comparatively an open 

 field, and had not undergone the wide and close explora- 

 tion which they had done when Mr. Burnham com- 

 menced his work. He has had, it is true, the advantage 

 of instruments of the finest class, and we may believe an 

 unusually acute vision ; but he must have exercised an 

 extraordinary and most meritorious amount of patience, 

 perseverance, and care in the discovery and accurate 

 measurement of such a list of double stars, and it will be 

 gratifying to the astronomical world that such well- 

 directed exertions have met with so exceptional a success. 



Among the more noteworthy stars included in Mr. 

 Burnham's new Catalogue (the fourteenth), which may be 

 considered a continuation of that published in vol. .xliv. 

 of the same Memoirs, the following may be mentioned: — 



X. 126 Tauri {li 1007), "a most remarkably close and 

 difficult pair, one of the closest knoan" ; magnitudes 6'o 

 and 6'2. With a power of 1400 there was only a slight 

 elongation. 



2. B..A.C. 346; Mr. Burnham thinks the principal star 

 may be variable, and he is certainly correct in his surmise. 

 Heis gives it as a naked-eye star 67 m , Gould 7'om.,and 

 it has been several times noted 8 m ; while the writer has 

 recorded it as low as 9 m. 



3. /3 117; a star with a proper motion, according to 

 Argelander, of o'-438 ; measures in 1S83 show a common 

 motion of the components ; their distance is 2"-2. 



4. f Sagittarii ; detected by Winlock, probably a retro- 

 grade motion of 225° in less than fourteen years ; and 

 evidently a change of 48^ in less than three years, by Mr. 

 Burnham's measures alone. It is an object for large in- 

 struments in the other hemisphere. 



5. /3 Delphini (/3 151). — A very rapid binary ; since its 

 detection by Mr. Burnham in 1873, there has been an 

 increase in the angle of about iSo', and a diminution in 

 distance from o"'6 to o"'25. He thinks " it may prove to 

 have, with the single exception of S Equulei, the shortest 

 period known." 



Mr. Burnham collects the measures of S Equulei, and 

 infers a period of revolution of about io'8 years. Measures 

 should be easy again in 1S85. 



6. 85 Pegasi yfi 7;^}). — The close pair was not mea- 

 surable in 18S2 ; the angle was about 333^ at the epoch 

 188375. 1 he mean annual motion is about 12''S, at which 

 rate the period would be le;s than thirty years. 



In the introduction to the Catalogue will be found 

 references to the publicatio.is where the thirteen previous 

 ones are to be found. 



MEASURING THE AURORA BOREALIS 

 T^HE study of the height of the aurora borealis above 

 -'■ the earth's surface is, it will be easily conceived, of 

 the greatest importance in understanding the nature of 

 this {.henomenon. Unfortunately the height of the aurora 

 has alwa\s been, and is to some extent still, a moot point 



