•B REPORT 1864. 



planet, the author had heard the same eminent person express views almost 

 identical Avith those flo-wdng fi'om the observations of Bessel and Johnson. At the 

 same time, the simplification which the author endeavoured to introduce into the 

 theory of the Earth's figm-e will not, if aiDplied to that of Mars, suffice to accoimt 

 for the usually received high cUipticity oi that body. Abstaining, for the present, 

 from any attempt at an explanation of this pecidiarity, let ua endeavour to trace 

 out its consequences ^vith reference to the configuration of that planet. It seems 

 to he generally admitted that there is, in the neighbourhood of one of the poles of 

 'Mars, a great mass of brilliant matter, analogous to a mass of terresti-ial snow. 

 This very sidostance is even supposed, ■ndth gTeat probability, to seriously inter- 

 fere with the accm-acy of telescopic observations, owing to the optical disturb- 

 ances arising from the in-adiation of such an extremely bright object. It is also 

 manifest that, if this substance should be snow, the vtimng seasons of the planet 

 would cause its dimensions to vary, and thus the power of the disturbing in- 

 fluence. These circumstances show that great caution should be used in accepting 

 any results which are liable to be afffected by the presence of this snowy patch, 

 and they also necessarily imply the existence of a fluid like water in that part of 

 the smface of Mars wherever the temperature is above the fi'eezing-point of the 

 fluid. If this shoidd be so, the geuerallj' assumed large ellipticity of Mars should 

 be followed by another residt. Several years ago, when controverting and dis- 

 proA-ing an erroneous theory of the Earth's figm-e, put forward by Plaj-fair, and 

 which has since acquired some importance by being reproduced by Sir John 

 Herschel, in support of his general views, and appealed to by Sir Charles Lj-ell, 

 the author obtained mathematical expressions for the equilibriiun of a fluid like 

 water spread over an exterior abraded spheroid such as this theory assumed the 

 Eai'th to be. It follows from these expressions that if the Earth possessed a very 

 small ellipticity, or were spherical, it woidd consist of two gi-eat circumpolar 

 continents, with an intermediate belt of equatorial ocean. He has assigned the 

 dimensions of these continents, supposing the ocean to have its present volume. 

 It also immediately follows that if the Earth had a very great ellipticity, such, 

 for example, as that so frequently assumed for Mars, the reverse would take place, 

 and the diy land would foi-m an equatorial belt, while the poles would be 

 enveloped in water. The dimensions of these circumpolar oceans, with the 

 assumed ellipticity of Mars, could be also assigned, and they should exist on its 

 surface, imless there should be great in-egidarities in the density of the matter 

 composing the planet. The mechanical theory on which these conclusions are 

 based is simple, and therefore the attention of obsen-ers may be directed to the 

 inquiry as to whether, compared with oiu- Earth, a greater predominance of dry 

 land exists at the equatorial parts of Mars compared to its polar regions. If the 

 author might venture to draw auy conclusion fi-om the results hitherto obsen-ed, 

 and especially from the dia'^'ings appended to Mr. Lockj-er's paper, in the 

 ' Memoirs of the Astronomical Society',' he would say that no such predominance 

 of equatorial land exists on the smfaee of Mars, and therefore if its appearances 

 are partly due to the presence of a liquid on its surface, we must conclude that ita 

 ellipticity has been generally exaggerated, and that the results of Bessel and 

 Johnson's observations are, upon the whole, nearer to the truth than those of 

 other observers. 



Sjpeculatmis on Physical Astronomy. By R. W. Hardy. 



On an extensive Lunar Plain near the Monies Hempiii, which it is jyroposecl to 

 name Otto Struve. By Dr. Lee, F.R.S., F.G.S. 

 The paper which the author presented to the Section was intended as a supple- 

 ment to those already brought before the Members of the Britsh Association by 

 the Eev. T. W. Webb "and Mr. Eirt. After alluding to the three large and beautifid 

 drawings of the Mare Crisium by Professor Piazzi Smyth, Dr. Lee called attention 

 to a large plain in the north-east quadrant of the moon, foimerly designated 

 " Lichtenbcrg " by the Hanoverian astronomer SchriJter. It is situated betwee}i two 

 mountain-chains, to the easternmost of which the German solenographers, Beor and 



