38 Reviews — Concretions, Auckland Harbour. 



III. — Concretions in the Recent Sediments op the Auckland 

 Harbour, New Zealand. By J. A. Bartrum. Trans. New 

 Zealand Inst., vol. xlix, pp. 425-8, with 1 plate, 1916. 



DURING the dredging operations of Auckland Harbour a number 

 of calcareous concretions were brought up by the pumps. 

 These consisted of nodular masses of hard, compact limestone, 

 varying in size from ^ in. up to 6 inches or more in diameter. 

 They enclose recent shells of all kinds, some of which seem to have 

 served as nuclei for the precipitation of the calcium carbonate, and 

 also diatoms and quartz grains. They give no indication of having 

 been derived from any previously consolidated rock, and seem to 

 have been formed contemporaneously with the harbour silt, by 

 precipitation of calcium carbonate from the sea-water. This 

 precipitation was probably occasioned by the decay of organic 

 matter in the epidermis of molluscs, or the hard parts of crabs which 

 form the nuclei of the concretions. 



W. H. W. 



IV. — The Jurassic Ironstones of the United Kingdom, Economically 

 considered. By E. H. Hatch. Journ. Iron and Steel Inst., 

 vol. xcvii, pp. 71 — 120. 



Average Analyses of British Iron-okes and Ironstones 

 produced in 1917-18. By F. H. Hatch. Published by the 

 Ministry of Munitions. 12 pp. 1918. 



AN important part of the work of facilitating the supply of 

 munitions of war lies in the proper development and economical 

 utilization of raw materials. In the case of iron-ores the Ministry 

 was fortunate in securing the services of Dr. Hatch to assist in 

 supervising these matters. Besides the actual mining of the ores it 

 was found that other subjects were also in need of attention, such 

 for example as " blending " of ores of varying composition to produce 

 a standard product, methods of calcining, and economies in transport. 

 All of these are briefly touched on in the first of these memoirs, but 

 the greater part of it is taken up with a description of the actual 

 occurrences and mining of the Jurassic ironstones of the British 

 Isles, with analyses and statistics of production. 



The Jurassic iron-ores occur at three principal horizons, namely, in 

 the Lower Lias in Lincolnshire, in the Middle Lias in Cleveland, 

 Leicestershire, and Oxfordshire, and in the Inferior Oolite in 

 Northamptonshire. Expressed in percentages of the Jurassic out- 

 put the Lower Lias was responsible in 1917 for 223 per cent, the 

 Middle Lias for 51 per cent, and the Inferior Oolite for 26-2 per cent. 

 The Upper Lias ore of Raasay amounted only to 65,985 tons or 

 0'5 per cent of the total. The Corallian ores of Westbury are not 

 now worked. 



The most striking recent development is in connexion with the 

 Middle Lias ores of Oxfordshire, which are now being exploited on 

 a very large scale, largely for the supply of furnaces in South Wales. 

 The total output of this county in 1917 was 434,435 tons, with an 

 average iron content of 24 per cent. 



