404 Transactions. — Geology. 



bottom or bed-rock, especially where the bed-rock is soft and 

 porous. The gold so found could not by any conceivable 

 process have got there except in solution." In gold-digging 

 this is a very simple every-day experience. If a ground- 

 race for sluicing golden dirt is made across ground that does 

 not contain gold, under the conditions given (a soft porous 

 rock), the fine shotty gold will work down in the rock not 

 only Sin. or lOin., but in many cases more than twice that 

 depth ; and the process can be seen. The water penetrates 

 porous places, softening and sometimes removing some of the 

 lighter material they contain, thus allowing the fine round 

 gold to sink ; and gold may be obtained as far as this action 

 has gone, but not farther. 



8. " That, if the gold in the deep placers had come ready 

 formed from the vein-matter in the reefs, it would be dis- 

 tributed in layers of unequal richness through the bed — the 

 richness depending on the amount of deposition taking place 

 at anv one time — and would not occur in increasing richness 

 from top to bottom." Professor Egleston, who points out this 

 argument, has evidently no knov,'ledge of how drifts are 

 formed. In the first place, the layers are of unequal rich- 

 ness, and naturally get poorer and the gold lighter upwards 

 from the bottom. The richness of the layer does not so much 

 depend on the amount of deposition at one time as on the quan- 

 tity and quality of the debris passing over, and from which 

 the deposition has been made. Take the Maitai Eiver, for 

 instance, and suppose the rock it has cut through and washed 

 away to have been gold-bearing down to its present level ; 

 then let an obstruction occur at the lower end, causing a 

 layer of gravel to accumulate all up tlie valley. At this level 

 the river might run for ages, depositmg whatever gold and heavy 

 mineral might be washed into it. The accumulations and 

 running-levels might go on indefinitely, but in each succeeding 

 level there would be less gold per ton, and of a lighter descrip- 

 tion, for these reasons : that the bottom layer would have all 

 the gold contained in the rock washed away in forming the 

 whole length, breadth, and depth of the valley up to the time 

 of the obstruction, concentrated into a narrow strip. Each 

 succeeding layer would cover a much wider area, and, even if 

 it contained the same number of ounces, would be much 

 poorer, as the gold would be dispersed through so much more 

 stuff. Another reason why succeeding levels would not be so 

 good is that only very light gold will travel over gravel ; so 

 that, with the creeks and feeders, most of the gold would 

 remain on the bed-rock above the junction with the layer. It 

 is a common thing on diggings for the gullies round a flat to 

 be payable and the flat too poor ; and in the case of the 

 Australian deep leads the original bottom levels, containing 



