NATURE 



\July 8, 1875 



the Dark Argus in Mr. Humphrey's book ; so would you kindly 

 inform me whether this is a new locality, and whether there are 

 two broods, the first in May and the second in July, as is the 

 case with several of family, as would appear from the above 

 statements? I identify the species with his Dark Argus by the 

 following peculiarities, viz. : (i) an obscure black spot near centre 

 of fore-wings ; (2) no black spots in the orange ocelli in fore- 

 wings, the hind-wings containing these black spots as in the 

 Brown Argus. John Hodgkin, Jun. 



West Derby, near Liverpool 



Meteorological Phenomenon 

 While walking out yesterday afternoon my attention was 

 drawn to a very remarkable display of mares-tail clouds spread- 

 ing from the north, stretching in broad and narrow bands in every 

 direction over the whole sky, and reaching beyond the zenith. 

 While standing thus facing the sun, I saw, at a great elevation, a 

 coloured bow with its convex red side towards the sun ; it was 

 only about one-sixth or one-seventh of a circle, and its width 

 seemed to be only about half that of an average ordinary rain- 

 bow. It had the appearance of being nearly horizontal, with its 

 centre not far from the zenith, but probably not so distant. Not 

 being accustomed to estimate elevations, when I got home I 

 took a quadrant and held it about the elevation of the part of the 

 bow nearest the sun, and found it came out, on repeated trials, 

 at a zenith distance of 25° or 26°.* When I first saw the bow it 

 was just 6h. 30m. P.M. Greenwich time, and the sun appeared to 

 be about 15° above the horizon (that you can correct by calcu- 

 lation). The sun was shining brightly, and the bowwus pro- 

 jected over a patch of sky slightly dimmed, at a great height 

 (but below the cirri?), by a smoke-grey haze; its ends just pro- 

 jected over the edges of the clouds. It lasted about 2m. 

 and then laded away. There was no halo or ring but this. The 

 wind was a rather fresh breeze, between S.S.E. and S. 

 Norwich, June 28 Henry Norton 



OUR ASTRONOMICAL COLUMN 

 St>Fi's Description of the Fixed Stars. — The 

 author of the ancient Uranometria to which we adverted 

 last week, Abd-al- Rahman al-Sufi. (an abbreviation of a 

 much longer name), was born in 903 ; he was of the sect 

 of the Sufis, and of Rai, a place to the east of Teheran. 

 He was in high favour with Adhad al-Davlat, of the reign- 

 ing family ot Persia, and it was principally for the instruc- 

 tion of this prince that he wrote the work under notice, 

 which was not the only one he produced. Ibn Jounis 

 reports that he was not only an observer, but framed astro- 

 nomical tables; and Dr. Schjellerup states he is known to 

 have undertaken geodetic operations. He is said to have 

 determined the length of the year, and in his tables fixes 

 the mean motion of the sun in the Persian year at 

 359° 45' 4o""2. He died in May 986. The prince Adhad 

 al-Davlat, who gave great encouragement to the study of 

 the sciences, commenced his reign in 949, and at the 

 time of his death, in 983, governed the extent of country 

 situate between the Caspian and the Persian Gulf. 



The translation of the " Description of the Fixed 

 Stars" by Sufi was made by Dr. Schjellerup from a 

 manuscript preserved in the Royal Library at Copen- 

 hagen, which came into the possession of Niebuhr in 

 1763. It is a copy made in 1601 from a manuscript 

 transcribed in 1013, and, as stated by Schjellerup, 

 " directement d'apres I'exemplaire de Sufi." The trans- 

 lation was finished when the Danish astronomer, through 

 Herr Dorn, had the opportunity of consulting another 

 copy of Siifi's work, recently acquired by the Imperial 

 Library of St. Petersburg. Where differences exist 

 between the two authorities, they are particularised in 

 notes to Schjellerup's translation. 



The description of the stars by Sufi, though founded 

 upon that of Ptolemy, is not merely a simple translation. 

 All the stars contained in Ptolemy's catalogue were 

 sought in the positions there recorded, and submitted to 

 attentive examination, and their magnitudes carefully 



* Subtended at my eye by bow and sun = about 50°? 



noted, as is distinctly stated by Sufi in his preface. 

 Schjellerup draws attention to the great extent of his 

 work, the perseverance displayed, and the minute accu- 

 racy and scientific criticism with which the whole is 

 executed ; so that, under all circumstances, the Persian 

 astronomer has presented us with the state of the sidereal 

 heavens in his time, which merits the highest confidence, 

 and which during nine centuries remains without a rival, 

 not having found its equal till the appearance of the 

 " Uranometria Nova " of Argelander. 



Prefixed to the description of the constellations, Schjel- 

 lerup has published what he terms " Tableau synoptique 

 de I'intensite lumineuse des ^toiles principals selon 

 Ptolemde (ou Hipparch), Sufi et Argelander," which is 

 obviously a valuable compilation, and one that may be 

 frequently consulted in cases where the naked-eye stars 

 are suspected of variability. The magnitudes attributed 

 to Ptolemy are not those given in our editions of the 

 " Almagest," but are taken from the work of Sufi ; indeed, 

 Schjellerup considers the former " parfaitement inutiles," 

 being expressed in round numbers and with much con- 

 fusion, so that in this respect also we have an important 

 addition to our knowledge of the magnitudes of the stars. 



In Siifi's tables of positions, the longitudes of the 

 Almagest are increased 12° 42', the latitudes being 

 unaltered. 



Generally speaking, there is a fair agreement between 

 the magnitudes of Ptolemy and Argelander, the differ- 

 ences not often exceeding a degree of the scale. Amongst 

 the larger discordances Schjellerup points to the cases of 

 25 Orionis and p Eridani, estimated by Ptolemy of the 

 third and fourth magnitudes respectively, while by Arge- 

 lander they are called a bright fifth and a sixth. Sufi's 

 estimates in the middle of the tenth century are inter- 

 mediate, the first star being rated a fourth and the second 

 a fifth magnitude. The case of Sirius is worthy of atten- 

 tion for another reason. Cicero, Horace, and other clas- 

 sical writers refer to the ruddy colour of this star. In the 

 editions of Ptolemy it is indicated as vnoKippos, but Sufi 

 makes no mention of this reddish tinge, though, as was 

 stated last week, other stars well marked as red stars in 

 our own day, are also so distinguished in his description 

 of the heavens. Instead of reading with Halma kuI 

 vwoKippos, Schjellerup thinks we should more correctly 

 read /cat aelpios, conformable to the designations which 

 Ptolemy gives to the other bright stars which bear a 

 proper name, as with a Bootis (apKTovpos), a Leonis 

 l^aa-iKia-Kos), &c. ; and remarks that it is certain Cicero 

 was the first who mentions the ruddiness of Sirius, that 

 Horace followed him, and that after Seneca we find no 

 reference to it. Eratosthenes, Aratus, Manilius, Hygmus, 

 and Germanicus are silent as to this particularity of the 

 star. 



The great nebula in Andromeda is named by Sufi as 

 an object generally known in the heavens, and it is inte- 

 resting to note that he also records the variable star 

 recently detected by Herr Julius Schmidt near a Virginis. 

 Its position is very clearly described. 



The title of Schjellerup's translation is " Description 

 des Etoiles Fixes, composde au milieu du dixieme siecle 

 de notre ere, par I'Astronome Persan Abd-al-Rahman al- 

 Sufi, par H. C. F. C. Schjellerup, St. Petersbourgj 1874." 

 It was presented to the Imperial Academy in June 1870. 



SOLAR RADIATION AND SUN-SPOTS 



SINCE I communicated to Nature the first results (vol. 

 xii. p. 147) of an examination of the Indian registers of 

 solar-radiation temperatures, I have examined some other 

 registers, all of which confirm the conclusion adumbrated 

 in my former note. Among these the most interesting 

 and striking is the hill station Darjiling, in Sikkim, 

 nearly 7,000 feet above the sea. The place is very 

 cloudy, being on the outer Himalayan range, and much 



