ASTRONOMICAL PROGRESS IN 1898. 



53 



large. As an observatory and expensive instruments 

 are not required, it has become a delightful pastime 

 for amateurs, and consequently the catalogue of 

 known variables has assumed immense proportions. 

 The number now known amounts to several thou- 

 sand. The cause of their variability has given rise 

 to much discussion. That the majority vary from 

 eclipses, total and partial, by dark satellites, is the 

 most rational theory that has been advanced. The 

 variations are from a fraction of a magnitude to in- 

 visibility, except with powerful telescopes. The 

 most surprising of all is the finding of 310 variables 

 in the cluster Messier 3; one ninth of all the stars 

 in the cluster vary in brightness. Prof. Pickering 

 records the discovery of 3 variables in the southern 

 sky, their fluctuations being detected by examina- 

 tion of their spectra. At the Cape of Good Hope 

 Observatory 16 new variables ware lately discovered. 

 Stanley Williams, in " Astronomische Nachrichten," 

 Nos. 3440 and 3450, gives a list of 13 that thus 

 vary. Mr. Espin announces the variableness of a 

 star in right ascension for A. D. 1900, 20 h 29 m 55 s ; 

 declination north, 54 57'. It varies from ninth to 

 fourteenth magnitude, or practically to invisibility. 

 R. Carintc is a very interesting variable through 

 wide limits, though not in a very short time, like 

 many others. According to Prof. John Tebbutt, of 

 Windsor, New South Wales, it varies from a pretty 

 bright star to complete invisibility without a tele- 

 scope. In four months and fifteen days it decreased 

 from the 4.9 magnitude to 9.3. It is exceedingly im- 

 probable that the fluctuations of this star can be 

 caused by an eclipse of one star by another. 



The photometric observations of U. Pegasi show 

 that a principal maximum alternates with a second- 

 ary minimum, the light curve closely resembling 

 that of Beta Lyra. The period is 8 h 59 m 41 8 , which 

 diirers from Dr. Chandler's value of 5 h 32 m 15 s ; but 

 it is pointed out that 16 half periods are nearly 

 c % qual to 13 of Chandler's, each being just less 

 than three days. Hence, Omega Centauri 19, with 

 a period of 7 h ll m . now displaces U. Pegasi as hav- 

 ing the shortest period known. 



Celestial Chemistry. Within the past twenty- 

 five years the splendid discovery of spectroscopy, 

 aided by great improvements in photography, the 

 increased size of telescopes, and the adoption of 

 electric appliances, has given rise to what may be 

 called a new astronomy. The uses of the different 

 varieties of spectroscope are many and varied. 

 There are four forms of the instrument the pris- 

 matic camera: the slit spectroscope, used with the 

 telescope as an analyzer; the slit spectroscope, used 

 without a telescope, as an integrator : and an ana- 

 lyzing spectroscope, used without a slit. 



During total eclipses of the sun the spectroscope 

 has solved several disputed points, notably the cause 

 of the "flash," or reversing layer, as Prof. Young, 

 its discoverer, calls it a beautiful phenomenon 

 which appears just at the beginning of totality, 

 when the rapidly narrowing strip of continuous 

 spectrum is invaded by a series of bright points, 

 which shine for an instant as a crowded series of 

 bright little colored arcs after the continuous spec- 

 trum has gone, and disappear, in their turn, a second 

 and a half later. The same phenomenon, but in 

 opposite order, is seen at the end of totality. There 

 is no doubt, says Prof. E. W. Maunder, of London, 

 as to the meaning of that short-lived phenomenon. 

 It represents a region of glowing gas, extending to 

 a height of about 700 miles above the solar surface. 

 So much seems clear. The debatable point is the 

 relation of these gases to the dark lines which are 

 found in the spectrum of the solar disk. The liter- 

 ature of the subject is extensive, involving the dis- 

 cussion of two theories, which can not be dealt with 

 here. 



Celestial Photography. At the Meudon Ob- 

 servatory, France, the nebula: are being photo- 

 graphed by a reflector of one metre aperture and 

 three metres in focal length, which reveals some 

 singular and unexpected results. The ring nebula 

 in Lyra was taken with an exposure of twenty, 

 thirty-five, and fifty-five minutes. The nebulosity 

 in the interior increases in brightness and density 

 with the length of exposure, while the diameter of 

 the ring increases but very little. An exposure of 

 fifty minutes on the planetary nebula in Aquarius 

 shows an appendage surrounding it resembling the 

 ring of Saturn. A photograph of the Pleiades 

 shows additional streamers of nebulosity. 



In "Monthly Notices of the Royal Astronomical 

 Society," No. 7, 1898. Isaac Roberts,thcdistinguished 

 celestial photographer, has a seven-page article on 

 the photograph of the nebula; in the Pleiades and 

 surrounding stars, with an exposure of ten hours, 

 accompanied with two half-tone illustrations. The 

 long exposure of course overexposed the brighter 

 stars, but it brought to light many thousands of 

 stars never before revealed to human eyes. It 

 shows the Merope nebula and the others hereto- 

 fore seen by the telescope, and additional to these 

 it shows numerous nebular streaks invisible with 

 the telescope, and, what is singular if they are not 

 results of some defects in the camera, they are 

 all nearly parallel with each other. He is of the 

 opinion that the bright stars, as we see them, have 

 no connection with the nebula 1 , but are simply de 

 picted on the nebulae, which may be either beyond 

 the stars or this side of them. He is also of the 

 opinion that the streaks have no connection with 

 the flocculent nebula', but are nebula? seen nearly 

 edgewise. It seems incredible that so many flat- 

 disk nebula? should, on so small an area of the sky, 

 have their edges so nearly parallel to our line of 

 sight. In his description of this remarkable ad- 

 mixture of nebula? and stars he makes no mention 

 of the new Merope nebula seen by mammoth re- 

 fractors. The old Merope nebula is of the streaky 

 character, with the star (a naked-eye one) in the 

 center of the denser part. Electra does not seem 

 to be involved in nebulosity, but there is a streak 

 of strong nebulosity extending 14' of arc from it. 

 Alcyone is involved in nebulosity, both of the 

 streaky and flocculent kinds, the streaks crossing 

 those of the Maia nebula without any apparent dis- 

 turbance or commingling. 



During the total phase of the eclipse of the Sun 

 Jan. 21, 1898, many photographs of it all along the 

 line of totality were taken, by comparison of which 

 many details of progressive changes were seen. 

 The great southwest ray on one plate extended 

 almost to its edge, three diameters from the Sun's 

 limb, or nearly 2,750,000 miles in length. An 

 attempt was made to photograph the zodiacal light, 

 but nothing was depicted on the plate after an 

 exposure of two and a quarter hours. Many photo- 

 graphs of the Milky Way and other regions rich 

 with stars, not visible from northern countries were 

 taken. One of the remarkable features of the 

 scheme was the immense size of the field the 

 Dallmeyre lens gave, which covered fully 40" 

 in diameter, the first time, says Mr. Maunder, that 

 anything like so wide a field without distortion \vjis 

 ever made. It was a little stigmatic lens only H 

 inch in diameter and 9 inches in focal length. 

 It was also used on the corona during the totid 

 phase of the eclipse. The exposures of the star 

 fields were four and a half hours each. 



Mr. Loewy's " Annual Report of the Paris Ob- 

 servatory" for 1897 has lately been published, and. 

 as usual, contains much interesting and instructive 

 information in regard to the work carried on at 

 that observatory. The great equatorial Coude has 



