16 Library. [Jan. 



be gained by the use of the stained collodion, tbougli the plates did show 

 some slight increase of sensitiveness for yellow. Fui'ther trials in copying 

 letterpress on yellow, green and red papers have given similar results, and 

 the only well-marked advantage of the stained plates for such work is the 

 great increase of density combined with clearness of the shadows, which 

 might be turned to useful account in cases where the increased length of 

 exposure is of no consequence. 



From these results it will be evident that the photographic action of 

 the spectrum is but a very slight index to the action of coloured objects, and 

 that methods have yet to be found which will enable us to overcome many 

 of the difficulties of colour still connected with the practice of photography. 

 The observations, however, have their value in showing that the photogra- 

 phic action of the spectrum is more extended than has usually been stated 

 and further investigation may lead to some useful practical application of 

 the principle of staining the collodion film. 



LiBRABT. 



Note. — It is proposed to adopt cm entirely new and improved arrange- 

 ment of the Library List, commencing tvith tlie present volume of the Proceed- 

 ings, but owing to delay in carrying out the new arrangement for the list of 

 additions received in December, it could not be included in the present 

 number of the Proceedings. The February number will therefore contain 

 the additions to the Library during December and January. — J. W. 



