ASTRONOMY, PROGRESS OF, IN 1892. 



37 



tablished that the decrease of heat had begun 

 quili' tlmv minutes In-fore first contact with the 



penumbra, a conclusion implying that the eartli's 



at mosphiTe is capable of exercising a dUtinot In -at, 

 al'.-orptioii at a height of ISM) miles. Prof. 

 Frank \V. Very, of the Allegheny Observatory, 

 Miught the solution of this problem in a differ- 

 ent manner, and, instead of choosing an eclipse, 

 observed tlie momi ill different phases, using a 

 bolometer in conjunction with a siderostat for 

 that purpose. The apparatus was so constructed 

 as to enable him to view the entire moon or but 

 a portion of it. lie adopted the latter method, 

 ami, the lunar image having been projected on a 

 white card in which a small hole had been pierced, 

 the image of the region whose heat was to be 

 measured was brought over this hole through 

 which the rays passed to the sensitive surface of 

 the bolometer. The results thus obtained are 

 given in ;i series of eight charts on which are 

 marked the different spots whose heat had been 

 observed ; corresponding tables give the meas- 

 ures, and isothermal lines inferred from these 

 measures are drawn on these charts. On the por- 

 tion of the moon to which the sun is setting the 

 heat gradient was found to be more steep than 

 on that part to which the sun is rising. The fol- 

 lowing are the main conclusions : 



1. The existence of a small heat-storing action by 

 which an excess of heat (not more than 10 per cent.) 

 is aivunmlated after many days of isolation seems to 

 be established. 



2. The circumferential zone of the full moon radi- 

 ates about 20 per cent, less than its center. 



8. Bright regions radiate only a little more than the 

 dark, though they reflect nearly twice as much. 



4. There is a somewhat larger proportion of reflect- 

 ed rays from the full moon than from the moon at first 

 quarter. 



5. The result obtained by Dr. Boeddicker as to the 

 different law followed by the diminution of heat from 

 that followed bv the decrease of light during an 

 eclipse, seems tol)C confirmed. 



Prof. Very, for his paper, was awarded the 

 prize offered by the Utrecht Society of Arts and 

 Sciences. 



Active Lunar Volcanoes. In the June num- 

 ber of "< Miservatory." IMS. Prof. William H. Pick- 

 ering has an interesting article from Arequipa, 

 Peru, March 28. 1892, entitled "Are there at 



I "resent Active Volcanoes on the Moon?" After 

 describing the atmospheric conditions at the ob- 

 servatory some 8,000 feet above tide, where a mag- 

 nifying power of from 800 to 1,200 may be used 

 to advantage, he discusses the question of active 

 volcanoes on the moon. Comparing his own ob- 

 servations with the chart of the moon published 

 by Neisen, he says : " Of a total of 67 craters, 32 

 wen- found common to both charts, 24 were 

 given by Neisen and not found by myself, while 



II were found that were not given by Neisen. 

 Using the 13-inch Clark telescope, all of Neisen's 

 craters were found save two, which could not be 

 found with a power of 800. The 11 other craters 

 found by myself were all confirmed and a great 

 number of other smaller ones were also seen." 



A committee's report to the British Associa- 

 tion, some twenty years ago. on the conspicuous 

 crater Plato, mentions 36 luminous points or 

 crater cones, No. 4 of which has entirely disap- 

 peared, only a whitish stain at present occupy- 

 ing its place. Nos. 7 and 31 are also missing, 



but eight miles southeast is a large crater not re- 

 ported by the committee. In class three as to 

 si/.e, out of the six m-nnlcd only one (No. 16) is 

 now visible. These facts, taken in consideration 

 wit lit ho falling in of the walls and the filling up 

 of the well-known crater Limn', may well suggest 

 the question heading this paragraph. 



It may be added that No. 4, alluded to above, 

 was seen as a conspicuous crater in 1880, 1882, 

 1887, and 1888. 



Comets. Since Oct. 2, 1891. the date of the 

 latest discovery of a comet given in our last vol- 

 ume, the following comets have been discovered, 

 named in the order of their finding rather than 

 their perihelion passages : 



Comet a (Swift) was discovered by Dr. Lewis 

 Swift, at the Warner Observatory, in the early 

 morning of March 6, in the constellation Sagit- 

 tarius. Though detected with a telescope, it was 

 visible (knowing its place) to the naked eye. It 

 is still (Oct. 14) visible telescopically, and has 

 proved a most remarkable body. As photo- 

 graphed on March 10 by Prof. II. C. Russell at 

 the Sydney Observatory, Australia, it showed 

 eight tails, two of which extended beyond the 

 plate. On the sides of these two long rays three 

 new streamers appear. All of these rays or ac- 

 tinic tails are easily seen on the photographic 

 plates, though none were visible to the eye with 

 the 11^-inch telescope. 



Prof. Barnard's photographs of the comet, 

 made at the Lick Observatory with an hour's ex- 

 posure, reveal, spreading out from the head, a 

 complicated system of a dozen tails, some of 

 which show remarkable curvatures. In less than 

 twenty-four hours the third tail had formed to 

 the extent of 10,000,000 miles, while the north- 

 ern one had entirely disappeared. His camera 

 was made to follow the comet, so that the stars 

 in the field are represented by lines instead of 

 dots. A picture secured on April 8 shows inter- 

 esting changes in the tails, a large protuberant 

 mass or semi-tail being seen on the southern side 

 of the principal branch, which developed into a 

 number of thin wisps not before noticed. On 

 one occasion the tail was twenty degrees long, as 

 seen by the naked eye. The following elliptic 

 elements have been computed for it by Dr. A. 

 Berberich, of Berlin : 



Time of perihelion passage, 1S92, April 6-C9025, Berlin 

 mean tune : 



Krom node to perihelion = 24* 81' 11-1" 

 Longitude of node = 240* 64' 15'4" 



Inclination = 88* 42' 20 6" 



Perihelion distance = 1-08606 



Kcrontrlcity = 0-998611 



While its eccentricity is indicative that it is a 

 periodic, yet its so near approach to a parabola 

 must give it a period of several thousand years. 

 Much uncertainty exists regarding the perio- 

 dicity of a comet whose eccentricity is so nearly 

 equal to 1. 



Comet b (Denning) was discovered by W. P. 

 Denning, at Bristol, Knglaml, in the constellation 

 Cepheus. on March 18,1892. It was excessively 

 faint, and has so remained. The following para- 

 bolic elements have been calculated by Dr. Ber- 

 berich : 



Perihelion passage, 1S92, May 11-22042, BrHn mean time : 

 Node to perihelion = 129' 18' 84-4" 

 ]x>nfUude of node = 258* 25' 41-6" 

 Inclination = 89*42' 4-8" 



Perihelion distance = 1-97064 



