MEAN DISTANCES OF THE PLANETS. 



243 



Temps for 1913,— these being the latest years pubHshed; if so 

 he will find the following figures : — 



Planet American Ephemeris 



Mercury o .387099 



Venus 0.723331 



Earth i .000000 



Alars I .523688 



Jupiter 5 .202803 



Saturn 9.538843 



Uranus 19.190978 



Neptune 30 .070672 



Connaissance 



des Temps 



o .387098 



.723330 



1 .000001 

 I .523678 

 5 -202555 



9-554751 

 19.217827 

 30.108980 



It is the writer's opinion that the first set is the correct set, 

 but the very fact that there are difi^erences shows that it is 

 necessary for astronomers to define more fully Avhat they mean 

 when they refer to the mean distance of a olanet. 



TRANSACTIONS OF SOCIETIES. 



Geological So-tiety of South Africa. — Monday. November 20th : 

 Dr. E. T. Mellor, President, in the chair. — "The intrusive rocks of the 

 Witwatersrand " : D, P, McDonald. The author began by desciibing' 

 typical examples of the intrusive rocks met with in the mines. Two 

 varieties of acid intrusive rocks may readily be distinguished, namely a 

 microgranite and a reddish-coloured granophyre. Rocks of intermediate 

 composition are apparently not very numerous : except for the sheets of 

 syenite or of tonalite, a pyroxene-andesite is the only rock examined which 

 can with certainty be placed in this group. The basic intrusive rocks 

 lielong to the two classes of dolerite and olivine-dolerite. The greatly 

 metamorphosed basic dykes were next examined in detail, and the con- 

 clusion expressed that the course of alteration had been considerably 

 affected by internal movement. With regard to the relative ages of the 

 intrusions, obviously the metamorphosed dykes were- the oldest, and the 

 microgranite intrusions must also be of early date. The second group 

 of intrusions includes the red granophyres, and the third the rocks of 

 most basic composition. — "The normal section of the Lower Witwaters- 

 rand System on the Central Rand, and its connection with West 

 Rand Sections " : Dr. E. T. Mellor. The author disagreed with the 

 accepted view that the wide differences between sections on the Central 

 and West Rand are due to original differences of deposition, and that 

 the Lower Witwatersrand System showed a great increase in thickness 

 towards the west. The differences referred to were ascribed mainly to 

 a system of strike-faults. The Elsburg beds, though unconformable to 

 the Lower Witwatersrand beds, are not necessarily so to the upper part 

 of the system, and there was not sufficient evidence for the removal of 

 the Elsburg beds to another system. The beds of the Lower Witwaters- 

 rand System appear to have been deposited un.der deltaic conditions. 



