518 Reviews — Silver Spur Mine. 



produced in it by varying weather conditions; the special object in 

 view was the comparison with the phenomena observed in oil-bearing 

 strata, but the results obtained are of much interest to all physical 

 and stratigraphical geologists. At Melbourne Beach, the place in 

 question, a broad stretch of stagnant fresh water, without visible 

 outlet, is separated from the open Atlantic by about half a mile of 

 blown sand, covered with palmettos and other scrub ; beneath this 

 is everywhere found artesian water. The sands of the open sea- 

 beach show several features of interest, including the ordinary types 

 of ripple-mark due to winds and waves such as are so often preserved 

 in older strata. The sloping part of the beach has an inclination 

 as steep as 5°, and it is pointed out by the author that an ancient 

 beach of similar slope, when exposed by denudation, might easily 

 be mistaken for one limb of a fold. Under certain wind-conditions 

 the beach sand is worked up into peculiar ridges called cusps by the 

 author. They seem to be formed when the wind is straight on 

 shore, and are destroyed by oblique surf-action. At times there are 

 found in the sand numerous clots of asphalt ; the origin of these is 

 not yet understood, since they are apparently not connected with 

 any local oil or bitumen occurrence, but appear to be washed up by 

 the sea. Another feature mentioned is the occurrence of masses of 

 a hard modern shell-limestone, called coquina ; these are formed 

 when a strong wind drives piles of shells into the hollows between 

 the cusps; these accumulations are sometimes as much as a foot 

 thick, and are soon hardened by cement deposited from percolating 

 rain and sea-water. In course of time these will form small slabs 

 and lenticles of limestone appearing abruptly in a coarse mechanical 

 sediment, a puzzling feature when observed in the older rocks. Just 

 below low-water mark the beach drops suddenly two or three feet 

 and forms a distinct channel extending one or two hundred yards to 

 the well-marked off-shore bar. This is the normal state of affairs, 

 but occasionally under special woather conditions the bar moves 

 inwards aud coalesces with the beach, obliterating the channel. 

 A description is also given of a very large shell-mound or kitchen- 

 midden, showing layers of wood-ash and occasional bits of pottery. 

 The mound is about 1,000 feet long, 50 feet wide, and 13 feet high 

 in the middle. Other mounds larger than this are known in other 

 parts of Florida, nevertheless this is impressive evidence of the 

 activities of the earlier inhabitants of the region. 



III. — Silver Spue Mine. Recent Development and Future Pros- 

 pecting. By L. C. Ball. Queensland Geological Survey 

 Publication JSTo. 264. pp. 36, with 10 figures. Brisbane, 1918. 



THIS mine, which is situated near the boundary between Queens- 

 land and New South Wales, on the Darling Downs, lies in 

 metamorphosed sediments and tuffs of Permo-Carboniferous age. 

 The ore bodies are found for the most part in crash zones in slate, 

 and consist of masses and disseminations of mixed sulphides, with a 

 gossan and oxidized zone at higher levels. The metals yielded are 



