ASTRONOMICAL PHENOMENA AND PROGRESS. 



49 



ers from 60 to 250. It was then a well-marked 

 though shallow crater, having a diameter 

 about three-fourths of that of Beer and Miid- 

 ler's Hipparchus F. The shadow of the 

 western wall was very conspicuous on the 

 floor of the crater. 



In a paper read before the British Associa- 

 tion, Baron von Madler makes a few sugges- 

 tions to moon-observers. He calls attention to 

 certain straights of light which- only show 

 themselves in high sun illumination ; of these 

 nothing is known, except that they are by no 

 means elevations. Ridges of only 500 feet 

 high are to be recognized through this shadow 

 near the light edges ; but these straights never 

 show the smallest shadow, and vanish in the 

 vicinity of the light edges. They proceed in 

 a radiating manner from single bright Ring- 

 mountains, especially from Tycho, Copernicus, 

 Kepler, Byrgins, Aristarchus, and Olbers; 

 from some other Ring-mountains they pro- 

 ceed only from one side, as from Menelaus 

 and Proclus. By a superficial observation 

 they may easily be confounded with the 

 mountain veins, but an attentive examination 

 will remark essential differences between 

 them. The easiest to observe is the light 

 straight which divides the Mare Serenitatis 

 almost equally in halves. He had observed 

 this several times for shadow, but could never 

 detect the smallest. The author alludes to 

 the rills on the moon's surface, as objects 

 whose variability, probably, does not depend 

 on our atmosphere, but is to be referred to 

 real changes. He had sought for two years 

 in vain for the southwest continuation of the 

 Ariadasus rill, though its existence came to 

 his knowledge from other quarters till, un- 

 expectedly, he obtained sight of it in 1833. He 

 remarks that it is advisable to observe on the 

 same evening, not merely a single rill, but 

 many somewhat similar ones; for as the 

 earth's atmosphere must exercise a like effect 

 upon them all, so would a perceptible varia- 

 tion present us with a hint for further investi- 

 gations. 



Heat given out ly the Moon. Mr. J. P. 

 Harrison, in a paper read before the Royal 

 Astronomical Society, takes the ground that the 

 heat acquired by the moon, and radiated to 

 the earth, is what Prof. Tyndall calls " dark 

 heat," or what would be almost wholly ab- 

 sorbed by our atmospheric vapor. This would 

 raise the temperature of the air above the 

 clouds, increase evaporation from their surface, 

 diminish their density, raise them to a higher 

 elevation, and under favorable circumstances 

 disperse them. In either case, a sensible fall 

 would take place in the temperature of the air 

 near the ground. This occurs at the period of 

 lunation when the moon has acquired the 

 greatest amount of heat it can receive from 

 the sun, which is when the half-moon then 

 illuminated has been subjected to solar radi- 

 ation for about 265 hours, or at the third or 

 last quarter. Opposite results will occur at 

 VOL. viii. 4 A 



the time of minimum heat in the moon. Ex- 

 periments to test the heat of the moon have 

 been made by Prof. C. P. Smyth, at Teneriffe. 

 He found that it amounted to no more than 

 would be given out by the heat of a wax- 

 candle at a distance of fifteen yards. Mr. 

 Harrison shows that this was not the right 

 time to have expected to discover heat from 

 the moon ; that at the time when most heat 

 was really given out, the effect upon the 

 earth's- surface was, that a lowering of the 

 temperature was produced. Mr. Harrison re- 

 fers to the tabulated results of temperature at 

 Oxford, Greenwich, and Berlin, ,taken for 

 several years, which agree in proving that, at 

 the time when by calculation the moon must 

 have acquired the greatest heat, the average 

 temperature of the earth's surface was lower, 

 accompanied by a dispersion of cloud. 



Solar and Planetary Tables. The Royal 

 Astronomical Society of England, at their 

 annual meeting in February, awarded the 

 gold medal to M. Le Terrier for his solar and 

 planetary tables, which include Mercury, 

 Venus, the Earth, and Mars, and have super- 

 seded others for calculating the places referred 

 to. 



Secular Variation of the Elements of the 

 Earth's Orbit. Mr. John L. Stockwell com- 

 municated to the American Journal of Sciences 

 for July an interesting paper on the "Secular 

 Variations of the Elements jof the Earth's Or- 

 bit" (see ANNUAL CYCLOPAEDIA, for 1867, art. 

 ASTRONOMICAL PHENOMENA AND PROGRESS). 

 Mr. Stockwell furnished a table, appended 

 hereto, based upon data and formulas more 

 fully given in his treatise on the "Secular 

 Equations of the Moon's Mean Motion." The 

 materials used in the preparation of the formulas 

 are those used in the construction of the Amer- 

 ican Ephemeris and Nautical Almanac, with 

 the exception of the mass of the earth, which 

 has been increased to 77T 1 T 57* The contents 

 obtained by Mr. Stockwell differ somewhat 

 from those given by Le Verrier in his Memoir 

 on the Secular Inequalities of the Seven Prin- 

 cipal Planets, not only on account of the dis- 

 turbing influence of the planet Neptune, which 

 had not been discovered at the time of his in- 

 vestigation, but also on account of the improved 

 values of the masses and elements of the other 

 planets. The superior limit of the eccentricity 

 of. the earth's orbit, which Le Verrier gives as 

 equal to 0.07775, should be reduced to 0.06939, 

 and an increase of the mass of the earth, cor- 

 responding to the latest determinations of the 

 solar parallax, would reduce the value of the 

 superior limit still more. 



In Mr. Stockwell's treatise on Secular Equa- 

 tions, etc., already referred to, he gave a table 

 and chart showing the eccentricity of the 

 earth's orbit during the period of a million of 

 years ; and the table here presented is merely 

 an extension of the former one. The first date 

 in the following table corresponds to 1,175,566 

 years before the year 1850, or to 1,100,000 



