37* SCIENCE PROGRESS 



of the geology, distribution, composition, methods of working, 

 and output of the Jurassic ironstones of the United Kingdom 

 (Journ. Iron and Steel Inst. 1918, 97, 71-125), the production 

 of which in 191 7 was over eleven million tons, with an average 

 iron content of 27*6 per cent. 



An iron formation, consisting of jasper, chert, haematite, 

 magnetite, siderite, and greenalite, of Pre-Cambrian age and 

 closely resembling the iron formation ol" the Lake Superior 

 region, has been found by E. S. Moore in the Belcher Islands 

 of Hudson Bay (Journ. Geol. 191 8, 26, 412-38). These rocks 

 are associated with thick sediments and basic lava flows, re- 

 sembling the Animikee and Keweenawan formations of Lake 

 Superior. There are also beds of a remarkable limestone, 

 consisting of concretions one to fifteen inches in diameter, so 

 similar to the modern concretions formed by blue-green algae 

 that there can be but little doubt that they are also of algal 

 origin. 



Broderick, T. M., The Relation of the Titaniferous Mag- 

 netites of North-eastern Minnesota to the Duluth Gabbro, 

 Econ. Geol. 191 7, 12, 663-96. 



Origin of Laterite. — In a comprehensive paper on laterite 

 J. M. Campbell (Mining Mag. 191 7, 17, 67-77 > 120-8 ; 171-9 ; 

 220-9) defines laterisation as the process by which the hy- 

 droxides of iron, aluminium, and titanium are deposited within 

 the mass of porous rocks near the surface. He believes that 

 unaltered or impermeable rock is incapable of being laterised ; 

 and that the process cannot take place when the rock is out of 

 contact with the atmosphere and vadose water. If by reason 

 of the erosion of a river valley a layer of laterite is left above 

 vadose water level it ceases to grow ; and this may be the 

 explanation of the frequent terraced arrangement of laterites. 

 On the other hand laterites which, owing to faulting, have 

 passed below vadose water level have their iron leached. Most 

 of the " bauxites " of commerce are believed to have originated 

 in this way. 



In a study of West Australian laterite Professor W. G. 

 Woolnough (Geol. Mag. 191 8, 3, 385-93) expresses the opinion 

 that laterite is essentially a product of low levels, and can only 

 occur in areas where drainage is practically at a standstill. 

 This condition generally means the existence of a peneplane 

 almost at sea level. Hence laterite upon a plateau, such as 



