550 



A^A TURE 



[October i, 1908 



Ephemeris jor Greenwich Mean Midnight. 



lyoS 



1 (true) 



& (inie) 



Ilrlgl.I- 



Oct. 1-5 ... 2132-4 ... +7258-4 ... 0-1249 ■•• 27 

 2-5 ... 21 iSS ... +72 5'0 

 3-5 ... 21 6-4 ... -f?! 6-9 ... 0-II70 ... 29 



L.1RGE Group of Sun-spots.— The large group of sun- 

 spols referred to in these colunins on August 13, and 

 again on September 10, has again been brought into view 

 by the sun's rotation, this making the third rotation 

 during which the same group has been seen. Its persistent 

 activity is evidenced by the fact that it is once more visible 

 to the' naked eye, although the separate spots seem to be 

 somewhat smaller and more scattered. 



The Orbit of f C.incri C. — The measures of f Cancri 

 made since J756 are brought together by Prof. Doberck 

 in No. 4273 of the AstronomiscJic Nachrichtcn (Sep- 

 tember 14), "and are supplemented by a few brief notes 

 concerning the orbit of the smaller component (C) of the 

 primary pair. 



It will be remembered that this system was the first for 

 which the existence of three coinponcnts was established, 

 the duplicate character of the larger star of the primary 

 pair being discovered by Herschel in 1781. Subsequent 

 observations showed that 'the motion of C is very irregular, 

 and led to the suspicion that this star is accompanied by 

 a dark companion. Independent evidence of the existence 

 of this invisible companion is deduced by Prof. Doberck 

 from measures made by Profs. Burnham and Barnard 

 between i8qi and 1005. 



He also finds that the star C moves round the centre 

 of gravity of C and D (the dark body) in a circle of 

 o"-i58 radius, the period being 17-43 years. .Assuming 

 the combined mass of A and B to be equal to that of the 

 sun, it follows that the relative masses of A, B, C, and D 

 are 0-5, 0-5, 0-62, and 0-43 respectively. 



Search-ephemeris for Comet TempeLj-Swift. — A con- 

 tinuation of the ephemeris, published by M. E. Maubant 

 in No. 426q of the Astronomische Nachrichten, for the 

 comet discovered by Tempcl in i86q is given below : — 



Three cphemerides are given, that from which the above 

 is taken being computed for the mean date (September 

 30-.S8)'for perihelion passage. According to the above, the 

 comet should be some 2° S. of Castor on October 6, and 

 about 45' N. of Pollux on October 9. 



The Maxor.\ Ob.servatory. — According to a note pub- 

 lished in No. 400 of the Observatory (p. 362, September) 

 the Manora Observatory, the instruments of which were 

 recently announced for sale, has been purchased by an 

 anonymous person, who invites observers of all nations 

 to observe with the equatorial. 



A Nebulous Field in Taurus. — In the September 

 number of the Bulletin dc la .Socit'(<? astronomique de 

 France (p. 400) Prof. Barnard has an interesting dis- 

 cussion of an extensive nebulosity, which he has photo- 

 graphed, in the constellation Taurus. 



A splendid reproduction accompanies the note, and 

 shows the peculiarities discussed. These consist of long 

 dark lanes, in an otherwise nebulous region crowded with 

 stars, apparently devoid of both stars and nebular matter, 

 and Prof. Barnard discusses the hypothesis th.nt their 

 appearance is caused by the interposition of absorbing 

 material between the background of nebula and stars 

 and the earth. He finds this explanation difficult to 

 embrace, but so far is unable to offer a more reasonable 

 one. The field covered by the photosrraph lies betwien 

 R.A. 4h. om. to 4h. 34m., and dec. 4-24° to -1-28°. 5. 



NO. 2031, VOL. 78] 



THE ISOTHERMAL LAYER OF THE 

 ATMOSPHERE. 



'T'HE important discussion of which we give here a 

 detailed iucount was organised b>' the committee of 

 .Section A of the British Association, and took place at 

 the recent meeting. 



It was intended that M. L. Teisserenc de Bort should 

 open the discussion, but he was unable to be present, and 

 sent the following communication : — 



Permit me to open the discussion on the isothermal 

 layer and the inversions of temperature which are found 

 there by recalling in a few words the results obtained 

 during the past twelve years. Our experiments at Trappts 

 have shown, in the first place, that the temperature ceased 

 to diminish at a certain height after having passed 

 through a point of maximum rate of decrease about 3000 

 metres lower down. 



The altitude at which the diminution ceases changes 

 with the character of the weather ; it may descend as low 

 as 8 kilometres at Paris during a cyclone, while it rises 

 as high as 13 or 14 kilometres in high-pressure areas and 

 in front of large cyclones. 



I indicated these peculiarities for the first time in 

 October, ic)oi. in a communication to the Luftscliiffart 

 A'erein at Berlin, then in a communication to the Meteor- 

 ological Society of France in March, 1902, and I developed 

 these conclusions in a note to the Acad^mie des Sciences 

 in April, 1902. 



A short time after, in the early part of May, ic)02. 

 Prof. Assmann showed from the ascents of six rubber 

 balloons that not only w-as there a cessation of the decrease 

 of temperature, but also an inversion. This inversion had 

 also been very marked in the first ascents by Hermite and 

 Besan^on, but Prof. Assmann .sought to explain it as 

 being due to the effect of solar radiation on the thermo- 

 meter, while the ventilation produced by the rapid ascent 

 of the balloon showed that it could not be referred to such 

 an error in the thermometer record. 



Having once demonstrated the existence of this iso- 

 thermal laver for places in the neighbourhood of Paris, 

 we sought to find the evidence of it in other regions in 

 order to show that it was a general phenomenon. Ascents 

 inade by us and our assistants in the winter of 1900-1, by 

 M. de Ouervain in Russia, by Mr. Eggenberger at Bath 

 in England in 1902, have made it evident that the pheno- 

 menon was a general one. On referring to the results of 

 the international ascents made in different countries, it is 

 seen that the cessation of the temperature decrease is 

 found in the case of all the balloons sent up, and that it 

 is impossible to refer it to insufficient ventilation, since 

 the phenoinenon was w-ell marked in ascents made during 

 the night. Since this time, ascents made on board the 

 Princesse Alice by Prof. Hergesell in 1905 have furnished 

 evidence of the existence of the layer near the Azores ; 

 ascents made in the United States by Mr. A. L. Rotch 

 have furnished evidence of its existence there with the 

 peculiarities I have indicated, i.e. high up over high- 

 pressure areas and low down over low-pressure areas. 



The expeditions of the Otaria, organised in conjunction 

 with mv friend Mr. Rotch, have proved the existence of 

 the zone in the tropics, and have shown that it is further 

 from the earth near the equatorial regions where the 

 trade winds meet. 



Finally, the ascents made at the end of the winters of 

 1907 and iqoS by the French-Sw-edish expedition organised 

 bv the Observatory of Trappes, with the support of Prof. 

 Hildebrandson, have shown that near the Arctic Circle, 

 at Kiruna, the layer exists and possesses _ general 

 characteristics analogous with those found in these 

 regions. 



The results of series of dally ascents for eight, ten, or 

 more davs in succession in February, iqoi, March, 1003, 

 and Mav, 1004, have proved that the change of altitude 

 of the point where the temperature ceases to fall Is accom- 

 panied bv changes of temperature of 10° C, 15° C, 20 C. 

 In an interval of a day or two at heights between q and 

 13 kilometres, variations great enough to be felt near the 

 surface during the same time. 



Thus the equalisation of temperature in the course of 



