230 Intelligence and Miscellaneous Articles. 



This angular distance is therefore determined once for all ; but 

 not so the form of the table of colours, which is independent of it, 

 since the same result can be arrived at with an infinity of triads. 



Which of the triads corresponds to the fundamental sensations ? 

 To answer this question we have no longer exact measures to guide 

 us, but only eye-estimates. It may in reality be enunciated thus : — 

 Are the colours for which the angular distance is the same equidis- 

 tant to sight ? If the answer is yes, all the triads have the same 

 value, and the table of the colours can be represented by a circle. 

 If, on the contrary, there are colours equidistant to sight whose 

 complementaries appear more distant from or nearer to one another, 

 the table of the colours presents angles. 



The study which I have previously made of the distribution of 

 the complementary colours in a chromatic circle shows incontest- 

 ably that all the colours comprised between the red and the orange- 

 yellow have complementaries very near the blue-green, and those 

 comprised between the blue and the violet-blue have their comple- 

 mentaries very close to the yellow. There are therefore vertices 

 towards the violet-blue and the orange. The difference appears to 

 me less accentuated for the third yellow-green. 



However it may be with the form of the table of colours, its pro- 

 jection upon the sides of an equilateral triangle has permitted the 

 determination of the exact angular distance of the colours — a result 

 which had not yet been obtained, and which suffices to connect the 

 facts at present known. The above diagram represents the law of 

 the mixture of colours, and may be substituted with advantage for 

 Newton's rule. 



It has moreover an aesthetic meaning : by the determination of 

 the triads it gives facility for applying to arrangements of three 

 colours the rules of harmony which I have given for the employ- 

 ment of complementary colours in decoration. — Comptes Rendus de 

 VAcademie des Sciences, July 2d, 1881, t. xciii. pp. 207-210. 



ON A METHOD FOR AMPLIFYING DISPLACEMENTS OF THE PLANE 

 OF POLARIZATION. BY M. H. BECQUEREL. 



When monochromatic luminous rays pass through a hcdf-ivave 

 crystal plate, the emergent rays are, as is known, rectilinearly 

 polarized in a plane which, in regard to the axis of the crystal plate, 

 is symmetric with the plane of polarization of the incident rays. 

 This property of a half-wave plate can be utilized for doubling and 

 trebling the measures of the displacements of the plane of polari- 

 zation of light. This can be accomplished especially in the follow- 

 ing manner : — 



Having arranged an experiment for the purpose of measuring a 

 rotation of the plane of polarization of light, the investigator com- 

 mences by fixing with the greatest care, by means of the analyzer, 

 the initial position of the plane of polarization of the incident rays. 

 A half-ivave plate is then interposed in front of the analyzer and 

 rotated until the plane of polarization of the light-rays is not de- 

 flected by their passing through the plate. In this position the 



