172 DISTRIBUTION OF BEDDED LEADS 



therefore, that in a shallow sea of very ancient date, in whicli 

 for the most part sandy sediment was deposited, irregularities 

 of current action or of depth of water, allowed mud to accumu- 

 late to a greater extent in isolated spots, alternating with the 

 sand. Later, when all the strata were folded into the well 

 recognized east and west undulations, those parts which had 

 the largest percentage of shaly sediment, being most plastic, 

 folded most and stood up higher as domes. Obviously, the}' 

 must be limited in all directions by sandy beds. The upper 

 limit has been largely worn away near the axes. The lateral 

 margins are visible today to anyone who searches for them. 

 The lower limit would be reached somewhere, by Ijoring. 



Comparison has often been made between our auriferous 

 beds and those of Bendigo — sometimes in a way iniconsciousl}' 

 to mislead us as to the true conditions here. This is one of 

 the cases in point. In Bendigo we have, not many isolated 

 domes each with its own problems, but one great dome, with a 

 single general pitch but with subordinate undulations. The 

 dome is composite, made up of several minor folds ; and these 

 folds have irregular plunges and dips. The leads, there as 

 here, lie in slate belts at or near the contact with sandstones ; 

 but there is a very constant relation between the lead and the 

 sandstone, which is lacking here — namely, the foot-wall is al- 

 w^ays sandstone, the hanging wall invariably slate. The most 

 marked dissimilarity between the two countries, however, is in 

 the fact that at Bendigo the vertical as well as the lateral dis- 

 tribution of the gold districts is indefinite ; and it is on just this 

 point that we seem to be led astray. Tlie large single dome of 

 wdiich we have spoken is, as was said, made up of a nund^er of 

 anticlines and synclines, striking north 16 degrees west, and 

 sometimes continuous along the strike for many miles. There 

 are 15 anticlines in about two miles of width, in the central 

 part of the 140 S(|uare miles of productive territor}', with an 

 average transverse interval of 800 feet from crest to crest of 

 the adjacent arches. The dips average 65 degrees ; and while 



