August 25, 1921] 



NATURE 



h2J 



agreeing with the normal white equation, agree with 

 it when the comparison white is diminished in 

 intensitj'. 



The facts in this article, whilst in complete accord 

 with those previously given ("The Physiology of 

 Vision," G. Bell and Sons, 1920), are inconsistent 

 with any theory of three fundamental sensations of 

 which the other colour sensations are compounded. 



Defects of light perception are quite distinct from 

 defective colour discrimination. All degrees of colour 

 discrimination may be classified as dichromic, tri- 

 chromic, tetrachromic, pentachromic, hexachromic. 



and heptachromic. This classification is fact and 

 not theory. For instance, the dichromic have two 

 colour sensations, red and violet, with a neutral divi- 

 sion in the spectrum. There are innumerable varie- 

 ties of dichromic vision, as there may be shortening 

 of either end of the spectrum or defects in the 

 luminosity curve. When the luminosity curve is the 

 same as the normal there is no evidence to show that 

 the perception of white is not the same as the normal. 

 I must express my indebtedness to Capt. Fulton 

 and Mr. Isaacs, of the Board of Trade, for their help 

 in making these observations. 



Regional Geology. 



OUR knowledge of the geology of England is 

 enriched by Dr. J. E. Marr's conception {The 

 Naturalist, February, 192 1) of Yorkshire as an earth- 

 block surrounded by down-folded strata, but with its 

 own Carboniferous series little disturbed, owing to 

 the rigidity of a pre-Cambrian mass beneath. The 

 block, which became tilted somewhat to the east, has 

 had an important effect on the drainage, and even on 

 the progress of ice-sheets, in northern England. 



A useful summary and map of the geology of 

 Jersey, by G. H. Plymen, appear in the Proceedings 

 of the Geologists' Association, vol. xxxii., p. 151 (1921), 

 a journal that has maintained its characteristic 

 features despite the difficult conditions following on 

 the war. The Geological Survey should find a ready 

 sale, even at the price of 105., for its " Short Account 

 of the Geology of the Isle of Wight," by H. J. 

 Osborne White (1921), which contains a coloured geo- 

 logical map on the scale of one quarter of an inch to 

 one mile. The second edition of the memoir that it 

 succeeds is now exhausted, and we must look back on 

 that handsome cloth-bound volume, issued at 85. 6d., 

 with the customary regret. But Mr. White's treatise 

 is not a mere abridgment of the older one, since he 

 brings to the work his wide knowledge of the south- 

 east of England, and of the literature of the inter- 

 vening thirty years. He adds original drawings, 

 showing the development of the surface and the rela- 

 tions of the rocks to well known scenic features, and 

 geologists who are fortunate enough to possess the 

 memoir bv Reid and Strahan must now add its 

 successor to their libraries before they start once 

 more for the island. Here, again, the question is 

 raised as to whether memoirs by public surveys should 

 be supposed to cover their own "cost of production," 

 or whether their dissemination should, as in Canada 

 and the United States, be regarded as a part of 

 public education. 



Dr. Arthur Winkler, as Ordnance-officer of the 7th 

 Gebirgsbrigadecommando, was stationed ^ at Santa 

 Lucia, near Tolmino, in 1916, and found time to ex- 

 tend F. Kossmat's researches on the central Isonzo 

 valley. He remarks, in the true spirit of science, that 

 the war had inflicted wounds on the mountain-sides, 

 and that many new exposures required registration. 

 His observations, continued in 1918, are now recorded 

 in a paper in the Jahrbttch der geologischen Staatsan- 

 stalt, vol. Ixx., pp. 11-124 (1920), illustrated by numer- 

 ous sections showing the Alpine folding of the strata, 

 from the Triassic limestones to flysch of Eocene age. 

 Glacial beds, dumped down into the valley, play an 

 important part in the dusty groove, and walls of 

 pebbly calcicrete are undermined by the green swirls 

 of the Isonzo. Above them tower the crags of con- 

 torted limestone, marked by brown scars where slabs 

 of rock have fallen away. Dr. Winkler's work brings 

 back happier memories than those recently associated 

 with the Bainsizza Plateau and Caporetto. 

 NO. 2704, VOL. 107] 



The Geological Survey of India issues a handsomely 

 illustrated memoir, by C. S. Middlemiss, on Idar 

 State, which lies on the tropic in the north-east of 

 the Bombay Presidency. Evidences of solar weather- 

 ing are given in the fine views of granite surfaces. 

 The main interest of the district lies in the junction 

 of the Delhi quartzite with the underlying series of 

 Aravalli schists and gneisses. Quartzite blocks again 

 and again appear to be stoped off into the Aravalli 

 rocks ; but the latter cannot in all cases be regarded as 

 igneous invaders. The author suggests that the 

 igneous masses which penetrate the Aravalli series 

 softened the metamorphosed sediments until they be- 

 haved as a semi-solid or plastic mass. The floor of Fin- 

 land seems to offer much support to his conclusions. 



Dr. W. F. Hume, untiring in his surveys of barren 

 lands, has issued, with his colleagues, a preliminary 

 report on Abu Durba (Western Sinai). This bulletin, 

 dated 1921, is No. i of a series on petroleum research. 

 The oil that is traceable at Abu Durba seems to 

 have been absorbed from shales into the Nubian 

 sandstone, and may originate (p. 11) in organic matter 

 wa'shed down with the shale-particles into the 

 Cretaceous sea. 



A. L. Du Toit (Union of S. Africa, Geol. Surv., 

 Explanation of Cape Sheet 28, 1920) traces in Pondo. 

 land the great monoclinal flexure that, as Penck 

 showed, is responsible for the edge of the plateau- 

 lands of south-eastern Africa. The down-folding has 

 determined the coast-line, and ceased about the close 

 of Cretaceous times. The inland region, however, 

 continued to rise, since Upper Cretaceous beds, near 

 East London, occur iioo ft. above the sea. The 

 shelves over which the rivers reach the sea represent 

 successive stages of the uplift. One is inclined to 

 ask once more : When was the great peneplain of the 

 plateau-surface formed? How has it escaped dis- 

 section inward from its Eocene edge? Has it been 

 perpetuated by wind-action in a region where rains 

 are only seasonal and droughts are more prevalent 

 than rains? 



The first pamphlet of the Geological Department of 

 Uganda (Entebbe, 1920) is written by E. j. Wayland, 

 and is intended to direct the attention of residents 

 to the interest of geological features. The prevalence 

 of laterite is discussed ; but we should hesitate to say 

 that the iron was "from the first" in the state of 

 hydrous oxide. Glauconite, mentioned in connection 

 with clays, is a silicate and not a phosphate. Are 

 not the cubic pseudomorphs in the argillites (p. 11) 

 more likely to have been originally pyrite than 

 rock-salt? The author introduces (p. 36) a useful 

 geographical term, arena, for undulating areas more 

 or less completely surrounded by hill-ranges. These 

 areas are shown to result from the denudation of 

 domes of strata, and rivers run through the sur- 

 rounding walls. The Woolhope inlier may thus be 

 called an arena, and numerous examples occur in the 



