ON THE ACTION OF LIGHT UPON DYED COLOURS. 285 



The Action of LigJit ripon Dyed Colours. — Report of the Committee, con- 

 sisting of Dr. T. E. Thorpe (Chairman), Professor J. J. Hummel 

 (Secretari/), Dr. W. H. Perkin, Professor W. J. Russell, Captain 

 Abney, Professor W. Stroud, and Professor R. Meldola. 

 (Drawn up by the Secretary.) 



The Report of the Committee presented this year refers to the results 

 obtained during the year 1896-97, in which period a large number of wool 

 and silk patterns, dyed with various natural and artificial brown and 

 black colouring matters, were exposed to iight. 



It is with regret that the Committee have to announce the deatli of 

 James A. Hirst, Esq., in whose grounds at Adel, near Leeds, all the 

 patterns experimented upon since 1892 have been exposed. Mr. Hii'st 

 took great interest in the work of this Committee, and the same interest 

 is shown by his son, E. A. Hirst, Esq., who has expressed the pleasure it 

 gives him in being able to aid in the continuation of the work. 



The general method of preparing the dyed patterns and the manner of 

 exposing them under glass, with free access of air and moisture, were the 

 same as already adopted in previous years. 



Each dyed pattern was divided into six pieces, one of which was pro- 

 tected from the action of light, while the others were exposed for different 

 periods of time. These ' periods of exposure ' were made equivalent to 

 those adopted in previous years by exposing, along with the patterns, 

 special series of ' standards,' dyed with the same colouring matters as were 

 then selected for this purpose. The standards were allowed to fade to the 

 same extent as those which marked o3 the ' fading period ' in previous 

 years, before being renewed, or before removing a set of dyed patterns 

 from the action of light. The patterns exposed during 1896-97 are, 

 therefore, comparable, in respect of the amount of fading action to which 

 they have been submitted, with the dyes already leported upon. 



The patterns were all put out for exposure on July 22, 1896, certain 

 sets being subsequently removed on the following dates : — August 22, 

 September 29, November 5, 1896 ; May 22, September 6, 1897. Of these 

 five ' periods of exposure ' thus marked off, periods 1 , 2, 3 were equivalent 

 to each other in fading power, whereas periods 4 and 5 were each equivalent 

 to four of the first period in this respect ; hence five patterns of each 

 colour have been submitted respectively to an amount of fading equal to 

 1, 2, 3, 7, and 11 times that of the first 'fading period' selected — viz. 

 July 22 to August 22, 1896. 



The dyed and faded patterns have been entered in pattei'n-card books 

 in such a manner that they can be readily compared witli each other. 



The following tables give the general result of tlie exposure experi- 

 ments made during 1896-97, the colours being divided, according to their 

 behaviour towards light, into the following five classes : Very fugitive, 

 fugitive, moderately fast, fast, very fast. 



The initial numbers refer to the order of the patterns in the pattern- 

 books. The S. and J. numbers refer to Schultz and Julius's 'Tabel- 

 larische Uebei'sicht der kunstlichen organischen Farbstoffen.' 



In the case of colouring matters requiring mordants, the particular 



