M 



ASTRONOMY, PBOORBB8 OF, IN 1806. 



HaDeyYall 



Ireot, and all bat that out belong 

 to UJ0lter group. 

 * 



This comet was de- 



54 11 . Though it has 

 to the Earth, it will not 

 *t 'perihelion until March, 1800, and 

 it ought, in strictness, to be included 

 fa) the list of oomets of that year. 



Twtai Eclipse of the Mooiu-On March 10, 

 im then ooonmd a total eclipse of the Moon 

 visible from both continent*. During the van- 

 ov* stage* of its progress it exhibited phenomena 

 of great interest. In coloration, the density of 

 the shadow, and the semiobscuration of the 

 dun nu totality it bore a great resemblance to its 

 last return, also total, in 1877. Several attempts 

 both short and long expo- 

 during the total phase, proved 

 One exposure of an entire minute 

 photographed only one faint, neighboring star. 

 t)M conspicuous feature of the eclipse was the 

 extraordinary brightness of A ri starch us, for 

 which its general high albedo seemed hardly to 



Erllie* of Sept. .1 and 4. 1 S9.-This total 

 ectipse of the Moon wasa return of that of Aug. 

 ft. 1877. In general appearance to the naked 

 eye it was very similar to that of March 10, 18M, 

 bwt with the telescope several marked 

 am were observable. Aristerchus, 

 glowed like a diamond, attracting universal at- 

 t^tion. was very faint and inconspicuous. At 

 the Ix>w Observatory, a phenomenon never be- 

 fore olawfud by the writer but visible to many 

 on this occasion was seen : the upper j 

 of the Moon was of a pale but deddeTblue color, 

 its upper boundary convex, agreeing exactly 

 with the convex are of the Moo7s limB. and the 



straigmv-not concave like the 

 narrow cresosnt The length of the 

 boat rV of the Moon*s diameter. 

 Twif feature was nicely observable with field and 

 oniam glass and with the U-ineh finder of the 

 JIBI. but was ls distinct, thouch easily 



chief value to astronomy of a total lunar 

 t b the determination of th,- times of 

 n of sters by the lunar disk during 

 Both limbs of the Moon being then 



' ' -'M - 



- - 1 -ft .... i. . .. of stars occulted 

 ascertainment of the Moon's diameter freed 

 from the efforts of irradiation is made possible. 

 Also, from diminution of the Moon's UgnMm* 

 fainter sters may then be seen near the disk t han 



at other times. At Greenwich Observatory 137 

 observations of disappearances or reappearances 

 were recorded by the eleven observers who 



...... ,,f the eclipse, Of this 



number of observations 124 were proix 

 good. In observing an occulution, the time 

 could be estimated to about the tenth of a 



The ruddiness of the Moon when totally im- 

 mersed in the Earth's shadow can, of course, be 

 understood, but no satisfactory reason has yet 

 been given for the great variation in color and 

 l.nllmncy in different eclipses. Even when hap- 

 ... ili. re is still 

 lifference in the amount of luminosity of 

 the eclipsed Moon. 



The raininess of the Moon during totality is 

 much underrated. IV. f. W. W. I'l.-k- -r 

 the total eclipse of 1887, estimated the eclipsed 

 Moon to be as much fainter than th' 

 as the latter was fainter than the Sun. This 

 must be an extreme view, however, as the best 

 authorities make the Sun 7(K),(KM) times as bright 

 as the Moon. 



With regard to the Moon's spectrum very little 

 has been accomplished. The atmospheric Lands 

 seemed so intense and broad that they practically 

 ran one into another, and observers simply got 

 the two ends of the spectrum cut <>iT. 



Variable Stars Algol. Dr. S. C. Chandler 

 explains the periodic variations in the intervals 

 between its minima by supposing that the bright 

 star with its eclipsing dark companion revolves 

 around a distant center of gravity, determined 

 by its relation to another dark body, during a 

 |N-riNl of 130-91 years. M. Tisserand considers 

 that t hey are caused by changes in the line of 

 apsides due to a polar compression of Algol. 

 This hypothesis require* considerable variation 

 in the duration of tin- minima: Dr. Chandler's, 

 that there should be a periodic inequality in 

 the proper motion of Algol. In " Astronomical 

 Journal," No. 843, Prof. Lewis Boss, of the Dud- 

 ley Observatory, at Albany, N. Y., gives a list of 

 observed positions of Algol and of 13 compari- 

 son stars for 1805-0, for the determination of the 

 truth or falsity of Chandler's hypothesis. If 

 correct, the apparent orbital motion of Algol is 

 now little less than at its maximum, and it will 

 so continue for nearly twenty-five years, within 

 which time it would be possible to truly deter- 

 mine the question. 



The variability of Z Jferculis was disc*, 

 by Dr. Chandler, in July. 1894, who regarded it 

 as a variable of the Algol type, with a per 

 8*23*50-. Its variability was detected V 

 wig also, who assigned it a period of only l d 23 h 

 55" 40. As, however, a minimum on Sept. 20 

 did not r*-eur at the time indicated by either of 

 these periods, iw. D une> concludes that the star 

 is of the V Cvgni type with nc M ua]]y bright com- 

 ponents, and that the faint and very bright alter- 

 nate in periods of forty-seven and forty-nine 

 The hypothesis demands that 7. Berculis 

 aowjfats of 2 stars of equal size, one of which is 

 twice as bright as the other; that they revolve 

 around their center of gravity in an elliptical 

 orbit whose semi ax is major is six times the di- 

 ameter of the stars ; that the plane of the orbit 

 passes through the Sun ; that the eccentricity is 

 0-3475; and that the line of apsides is inclined 



