May 5. 1892] NATURE 



23 



which is decomposed below the boiling-point of benrene, 

 Ethylaniline is easily acted on by the tetrachloride, ethylaniline 

 hydrochloride separates, and a compound having the compo- 

 sition Si(PhNEt)4 is formed. Diethylaniline is but feebly 

 acted on by silicon tetrachloride ; the compound PhNEtjHCl 

 is formed, and probably a substance of the composition 

 Si(C8H4NEta)4.— Chemistry of the compounds of thiourea and 

 thiocarbimides with aldehyde-ammonia, by A. E. Dixon. 

 The alkyl and allied thiocarbimides react with aldehyde- 

 ammonia, in accordance with the following equation — 

 R.NCS -t- 2R'CH(OH)NH, = CSN3H.,R(CHR'), + 2H.,0. 

 It was suggested that some connection might exist between 

 the class of substances so formed and the compounds obtained 

 by the action of thiourea on the aldehyde-ammonias. From 

 the great similarity in behaviour of the compounds derived from 

 the two sources, the author infers that they are members of the same 

 class. Though thiourea and aldehyde-ammonia readily interact, 

 it was found impossible, under any conditions, to cause sub- 

 stituted thioureas to act on aldehyde-ammonia. The author 

 considers that this fact indicates that the monosubstituted 



/NHj /NHR. 



thioureas are of the form HN iCq and not CS < 



^SH \NH, 



—The atomic weight of boron, by J. L. Hoskyns-Abrahall. 

 The deceased author determined the atomic weight of boron by 

 estimating the amount of silver necessary to precipitate the 

 bromine from a known weight of boron bromide. The mean 

 atomic weight obtained is io-8i6 ± o-cx355. Silver is taken as 

 107 923, and bromine as 79'9Si. 



Physical Society, April 8.— Dr. J. H. Gladstone, F.R.S., 

 Past President, in the chair. — Mr. Walter Baily read a paper on 

 the construction of a colour map. By the term " colour map," 

 the author meant a diagram, each point of which defines by its 

 position some particular colour. Captain Abney had shown that 

 all colours, except the purples, could be formed by adding white 

 light to some spectrum colour, whilst all except the greens could 

 be made to produce white by the addition of some spectrum 

 colour. There were, therefore, two ways in which colours, 

 other than greens and purples, could be indicated. In one of 

 these, the ordinate of a point might represent the spectrum 

 colour by its wave-length, and the abscissa, measured to the 

 right of a vertical spectrum line, the amount of white light to be 

 added to the spectrum colour to produce the colour represented 

 by the point. In the other, the abscissa of a point situated on 

 the left of the spectrum line represents the quantity of white 

 light produced by the addition of the spectrum colour to the 

 colour indicated by the point. Regarding the spectrum colours 

 as formed by mixing three primary colours (red, green, and 

 violet) in varying proportions, three curves were drawn to the 

 left of the spectrum line whose abscissae represented respectively 

 the proportions of the three primary colours present in the cor- 

 responding spectrum colour. Horizontal distances from any 

 point to these curves show the proportions in which the primary 

 colours are to be mixed produce to the particular colour defined 

 by that point. For points between the curves, the horizontal 

 distances are not measured all in one direction, and therefore 

 indicate abnormal or imaginary colours. The principle of the 

 map was farther illustrated by a sort of colour staff, consisting 

 of three horizontal lines representing the three primary colour 

 sensations (see figure) of such luminosities that equal lengths of 



Bed 



Green 



Violet 



A S 



^ A 



the three lines indicate white light. If points, R, G, v, be taken 

 in these lines, then a cross line A will cut off lengths A R, A G, 

 A V, whose mixture will produce a certain colour. If now A be 

 moved parallel to itself towards the right, the colour will 

 change by the addition of white light ; moving A to the left 

 means a subtraction of white light. When R, G, and V are 

 properly chosen, a certain position, s, of the cross line, corresponds 

 to a spectrum colour. The whole of the series of colours 

 which can be obtained by adding white light to that spectrum 

 colour can then be represented by sliding a towards the right. 

 Positions s' and a' give colours complementary to s and A. The 

 distinguishing features of such a series of colours are the 



differences R - G and G - V, and theauthor calls the ratio ^—^ the 



G-v 

 " colour index." Passing up the spectrum from red to violet, 

 NO. II 75, VOL. 46] 



the index, which is first large and positive, diminishes and 

 becomes negative between yellow and blue ; it then passes 

 through infinity, and becomes positive and decreases to zero. 

 The subject of determining the indexes of colours resulting from 

 the mixture in various proportions of two other colours whose 

 indexes were known, was considered, and diagrams showing 

 the various curves, exhibited. Experimental methods of 

 determining the proportions of the primary colour sensations 

 constituting the spectrum tints were described. A visitor 

 inquired how the author's system provided for the class of 

 colours outside the red and violet. He also desired a definition 

 of "white light." He himself had never been able to produce 

 pure white by mixture of colours, for a reddish violet generally 

 resulted. On the other hand, he found it possible to match any 

 other colour by mixture. Prof. Carey Foster thought 

 Helmholtz was the first to propound the law which the author 

 had attributed to Captain Abney. He wished to know how the 

 amounts of colour sensation were supposed to be measured. 

 White light he considered ought to be defined as light in which 

 a normal eye, not fatigued, could perceive no preponderance of 

 any colour. Mr. Blakesley said that if white light was a mixture, 

 and only two unknowns were necessary, then any colour could 

 be produced by the mixture of two other colours. Dr. Sumpner 



Eointed out that white light was by no means a constant colour, 

 ut depended greatly on the source. He thought the author's 

 map of a more absolute nature than that proposed by Maxwell. 

 Dr. Hoffert inquired whether the intensities of each spectrum 

 colour had been considered equal or otherwise taken into 

 account, and also whether the results arrived at would be true 

 for intensities other than those chosen. Mr. Baily, in reply, 

 said Captain Abney had found the light from the crater in the 

 positive carbon of an electric arc to be the most constant white, 

 and in his method of experimenting errors due to variations of the 

 source cancelled. The quantity of any spectrum colour was de- 

 fined by the breadth of the band used, the breadth being small and 

 measured on the scale of wave-lengths. — A paper on a mnemonic 

 table for changing from electro-static to practical and C.G. S. 

 electro-magnetic units was read by Mr. W. deed. In the 

 table, which is given below, the abbreviations Stat and Mag are 

 used to denote the electro-static and electro-magnetic units 

 respectively, and v stands for 3 x 10'" :— 



Units of 



Capacity. Resistance. Potential. Current. Quantity. 

 Powers of to for prac- 

 tical and magnetic 



units 9 ... 9 ... 8 ... I ... I 



Small unit Sut ... Mag ... Mag .. Stat ... Stat 



Practical unit ... Farad ... Ohm ... Volt ... Ampere ... Coulomb 



Large unit .~ ... Mag ... Stat ... Stat ... Mag ...Mag 

 Factor for Stat and 

 Mag ... ... v' ... t>» ... V ... V ... V 



To form the table, the numbers 981 in the middle of the second 

 line give the value of g. The end numbers are duplicated, 

 giving 99,811. Below them in the fourth line come the names 

 of the practical units, the initials forming the word fovac. 

 Remembering that the electro-magnetic units of resistance and 

 potential were too small for practical use, one places Mag above 

 both Ohm and Volt. Ohm's law and definitions then show 

 that the practical units of capacity, current, and quantity must 

 be less than the electro- magnetic units, hence Mag must be 

 written below Farad, Ampere, and Coulomb. Since the 

 practical units are intermediate in magnitude between Stat and 

 Mag, the vacant spaces are then filled in by Stat. The z^'s in 

 the bottom line are added from memory. Several examples 

 showing the use of the table are worked out in the paper 

 accompanying the table. — A paper on the law of colour in 

 relation to chemical constitution, by William Akroyd, was read 

 by Mr. Blakesley. The author has observed that, in cases of 

 compounds having a constant radical, R, and a variable radical R', 

 the effect of an increase in the molecular weight of R is to make 

 the colour of the compound tend towards the red end of the 

 colour scale. Exceptions are, however, noted. Mr. H. M. 

 Elder questioned the author's conclusions, saying that in many 

 cases the colours tend towards blue. 



Anthropological Institute, April 26.— Dr. Edward B. 

 Tylor, F.R.S., President, in the chair.— Prof. R. K. Douglas 

 read a paper on the social tnd religious ideas of the 

 Chinese, as illustrated in the ideographic characters of the 

 language. The paper begins with a short introduction, show- 

 ing that the Chinese ideographic characters are picture-writings, 

 and that as such they supply an interpretation of the meaning 

 of words as these were understood by the inventors of the 



