120 



NA TURE 



[May 31, 1888 



By taking the mean of the separate determinations for different 

 parts of the prismatic spectrum, Dr. Koenig had constructed a 

 •curve for the light-intensity of all the colours of the spectrum ; 

 there was a difference of at most 2 per cent, between the values of 

 the separate measurements and the mean. The speaker then 

 made similar measurements with his own normal trichromatic 

 ■eyes ; in this case he obtained a greater difference between the 

 value of the separate determinations and the mean (up to 5 per 

 cent.) but the curve of light-intensity for the whole range of the 

 spectrum was found to be identical with that obtained from Dr. 

 Broddahn. By reducing the prismatic spectrum used in these 

 experiments to one produced by diffraction, he was able to cal- 

 culate the curve of light-intensity for a normal spectrum. 

 Comparing this curve with those which he had obtained, in 

 conjunction with Dr. Dieterici, for the sensations of the three 

 primary colours, red, green, and blue (as determined for each 

 point in a normal spectrum), he found that the curve of light- 

 intensity of the spectrum was identical with that for the sensation 

 of red. From this it must be concluded that the sensation of 

 luminous intensity for each sepa> ate light is simply dependent 

 on the amount of red contained in it, or, to state this more 

 accurately, the brightness of each kind of light is determined by 

 the extent to which it stimulates the red-perceiving fibres of the 

 retina. Dr. Koenig had some time ago given expression to the 

 conjecture that in the dichromatic eye it is not the fibres for the 

 perception of the third colour which are wanting (the red-per- 

 ceiving for red colour-blindness and green-perceiving for green), 

 but that they are, so to say, differently tuned ; tuned down in 

 those who are colour-blind to green, so that they can only per- 

 ceive the sensation due to light as red, tuned up to a higher 

 pitch in those who are red colour-blind, so that when they are 

 stimulated by rays of greater wave-length they only perceive 

 g' een. It is now possible to verify the above conjecture experi- 

 mentally as follows. The measurements of luminous intensities 

 throughout the spectrum were made upon the eye of another 

 person who was colour-blind, and this time on one who was red 

 colour-blind ; in this case the curve obtained was identical with 

 that of the sensation of green. The phenomena observed by 

 Dove, that the relative luminous intensities of red and blue vary 

 according to the intensity of the illumination, were verified by 

 Dr. Koenig, but only up to a certain limit ; beyond this limit, 

 the relative luminosities of these two colours underwent no 

 further alteration in the brightness of the illumination. — Prof. 

 Gad discussed Prof. Fick's views on blood-pressure in the 

 capillaries, which the latter believed he had placed on an experi- 

 mental basis by means of an artificial vascular scheme ; accord- 

 ing to this the pressure in the capillaries could not be much less 

 than in the arteries, and only sinks appreciably as the capillaries 

 are passing over into the veins. Prof. Gad showed that the 

 conditions existing in the above scheme cannot be applied to the 

 blood-capillaries ; he further pointed out that the requisite data 

 for calculating the true blood-pressure in the capillaries can be 

 obtained from a theoretical consideration of the rate of flow in, 

 and sectional area of, these vessels, and from this the pressure 

 would appear to be about half of that which exists in the aorta. 

 A true basis for any theory of capillary blood-pressure can only 

 be obtained from such experimental investigation as admits 

 of being applied to various parts of the purely theoretical 

 consideration. 



Stockholm. 



Royal Academy of Sciences, April II. — Prof. W. C. 

 Williamson, of Manchester, was elected a foreign member of the 

 Academy. — Critical remarks on the researches of Foeppl on the 

 electrical conductibility of the vacuum, by Prof. Edlund. — A 

 theory of isohydric solutions, by Dr. Arrhenius. — Remarks on 

 the fossils of the Cretaceous formation of Sweden, by Prof. B. 

 Lundgren. 



May 9. — On Triglaps pingelii, an Arctic fish, found for the 

 first time off the shores of Sweden, and on some specimens of 

 Syrrhaptes paradoxus lately shot in Sweden, by Prof. F. A. 

 Smitt. — The whale of Swedenborg {Balana svedenborgii, 

 Liljeborg) found in the diluvial strata of Sweden, described by 

 Dr. Carl Aurivillius. — On the anazotic, stored up nutriments of 

 the Graminese, by Dr. C. J. Johanson. — A generalization of the 

 researches of Laplace on the libration in the orbits of the planets, 

 by Dr. K. Bohlin. — On the points of approximation in the theory 

 of perturbation, by the same. — Some extracts from the report of 

 the French scientific expedition to Spitzbergen and other places in 

 the years 1838, 1839, and 1840, by C. B. Lilliehook, R.N. — 



Contributions to the theory of the undulatory movement in a 

 gaseous medium (conclusion), by Dr. A. W. Backlund.— 

 Derivatcs of the 5-amido-naphthaline-sulpho-acid, by Prof. P. T. 

 Cleve. — Derivates of the 7-amido-naphthaline-sulpho-acid, by the 

 same. — On naphthol acids, by Dr. A. G. Ekstrand. — On ab- 

 normal forms of the first abdominal appendices of some female 

 cray-fishes, by Dr. D. G. Bergendahl. — On two new Lamelli- 

 branchiates from the Arctic post-glacial beds of Scania, by Herr 

 G. Clessin, of Ochsenfurth, Bavaria. 



Amsterdam. 



Royal Academy of Sciences, April 27. — Mr. J. A. C. 

 Oudemans spoke of Airy's double-image micrometer, and stated 

 the result of his efforts to discover the conditions to which this 

 apparatus must be made to conform, in order that the value of 

 one screw-turn maybe independent of the adjustment of the eye. 

 He had found that the distance from the first to the second lens 

 must be equal to the focal length of the first lens — a condition 

 already fulfilled in the micrometer for another purpose. 



BOOKS, PAMPHLETS, and SERIALS RECEIVED. 



British Petrography : J. J. Harris Teall (Dulau). — A Manual of Orchi- 

 daceous Plants, Part 3 (Veitch). — Longmans' Commercial Mathematics 

 (Longmans). — A Wanderer's Notes, 2 vols. : W. Beatty- Kingston (Chap- 

 man and Hall). — Principles of Agricultural Practice : J. Wrightson 

 (Chapman and Hall). — Discromatopsia, Enrico dal Pozzo di Mombello 

 (Scariglia, Foligno). — Soaps and Candles: J. Cameron (Churchill). — Die 

 Regenverhiiltnisse der Iberischen Halbinrel : G. Hellmann (Pormetter, 

 Berlin). — Proceedings of the Geologists' Association, February (Stanford). 



CONTENTS. pace 



Al-Biruni 97 



The Scientific Writings of Joseph Henry 98 



An Elementary Text-book of Physiology 99 



Our Book Shelf:— 



Le Conte : "Evolution and its Relation to Religious 



Thought" 100 



Slatter : " Outlines of Qualitative Analysis " . . . . 100 



Powles : " The Land of the Pink Pearl " 10 1 



Stevenson : "A Treatise on Alcohol, with Tables of 



Spirit Gravities" • 101 



Letters to the Editor : — 



The Dispersal of Seeds by Birds. —Dr. H. B. 



Guppy 101 



Nose-Blackening as Preventive of Snow-Blindness. — 



Dr. Robert L. Bowles 101 



Mysterious Sky Lights. {With Diagram.') — W. 



Mattieu Williams 102 



Curious Apparent Motion of the Moon seen in 



Australia. — T. Mellard Reade 102 



Another Specimen of Lepidosiren paradoxa. — Prof. 



Henry H. Giglioli 102 



Dreams. — E. H 103 



Strange Rise of Wells in Rainless Season. — E. H. . . 103 



Milk v. Lightning. — Rev. John Cyprian Rust . . 103 

 The Renewed Irruntion of Syrrhaptes. — Prof. Alfred 



Newton, F.R.S 103 



"The Shell-Collector's Hand-book for the Field."— 

 Dr. J. W. Williams ; Dr. Henry Woodward, 



F.R.S 103 



Freaks of Nature.— Major D. Erskine ; C. H. 



Erskine 104 



Whirlwinds, Waterspouts, Storms, and Rotating 



Spheres. {Illustrated.) By E. Douglas Archibald . 104 

 Timber, and some of its Diseases. VII. {Illus'rated.) 



By Prof. H. Marshall Ward 10S 



Ilerve Mangon in 



Notes 112 



Our Astronomical Column : — 



Comet 1888 a (Sawerthal) 114 



The Short Period Comets and Asteroids 114 



New Minor Planet 115 



Astronomical Phenomena for the Week 1888 



June 3-9 115 



Geographical Notes 115 



The Linnean Society 116 



University and Educational Intelligence 116 



Societies and Academies 117 



Books, Pamphlets, and Serials Received 120 



