Progress of Astronomy during the Year 1879, 445 
of tables, by which the approximate elements of any solar eclipse 
between b.c. 700 and A.D. 2300 may be found with a few minutes 
calculation, and by which any eclipse occurring during this 
period may be promptly identified. As an example of the use of 
the tables the celebrated eclipse, B.c. 584, is examined at the end 
of the paper. 
According to Natwre, a new discussion of ancient solar 
eclipses has been commenced under the auspices of the Smith- 
sonian Institution by Mr. D. P. Todd. The computations so far 
relate to the eclipses of Thales, Larissa, Ennius, Agathocles, and 
Stiklestad, 1030, and to two eclipses of the thirteenth century 
which have already been discussed by Celoria of Milan. 
The effect of the ellipticity of Mars on the motion of the sat- 
ellites has been investigated by Professor Adams (M.N., November). 
He shows that the ellipticity is probably between 7+; and 34, 
and that the angles between the equator of Mars, and the fixed 
planes of the inner and outer satellite are respectively less than 
l’andabout 1°. The ellipticity will produce rapid direct motions 
of the apses of the satellites, especially in the case of the inner 
one. 
No papers published during the past year exceed in importance 
those by Mr. G. H. Darwin on the secular effects of tidal friction 
on the configuration of a planet and its satellite.* In the first 
paper the theory of the deformation of a viscous or imperfectly 
elastic spheroid under the attraction of satellites is investigated. 
Numerical calculations show that bodily tides in the Earth are at 
present very small. From this point Mr. Darwin was led to con- 
sider the perturbed rotation of such a spheroid, and thereaction 
on the perturbing bodies. He has in the A. N. 2294 given the 
following summary of the results arrived at through these inves- 
tigations, which, no doubt, mark the beginning of a new era in 
our knowledge of the past history of the solar system :— 
1. The lunar period must have been shorter in the past, and 
may be traced back from the present 27:3 days, until initially the 
Moon revolved round the Earth in from two to four hours. 
2. The inclination of the orbit to the “ proper plane” must have 
* Three of these papers are published in the “ Philosophical Transactions” for 1879, a 
fourth one in the “ Proceedings Royal Society, No. 197,” while a fifth one was read to 
the Royal Society December 18th, 1879, and is as yet only known by an abstract in Nature. 
