DISCOVERY 



133 



the loss of light by absorption would be considerable, 

 and allowance would have to be made in constructing 

 the instrument for the displacement of the images 

 by refraction. 



These were the defects which prevented the further 

 development of the chromoscope and its application 

 to uses other than that for which it was originally 

 devised ; and, indeed, it seemed likely that the chromo- 

 scope would remain exclusively at the service of 

 colour photography. 



Quite recently, however, Messrs. Adam Hilger, in 

 the course of cunning research in optical fields of 

 science, discovered that an extremely thin and tightly 

 stretched film of celluloid served equally well as, in fact 

 much better than, glass as a transparent reflector. 

 Of a thickness little greater than the wave-length of 

 visible light, its sensitivity was put to use in their 

 optical synometer and various other instruments of 

 Adam Hilger design. All the defects inseparable from 

 the emplojTnent of glass mirrors were now eradicated. 

 But it was not until Adrian Bernard Klein, artist and 

 colour physicist, turned his mind to this discovery 

 that its application to the chromoscope came to light. 

 Adrian Klein, skilled in the matching and the music 



j of colour, knew the defects of the chromoscope ; and, 

 not slow to grasp the corresponding significance of 

 optical celluloid, caused a ten-picture instrument to 



i be built. In this instrument he made use of ten 

 celluloid mirrors in which the formation of secondary 

 images was successfully avoided. 



In this manner the chromoscope was freed from the 

 shadow in which it had lain for sixty years, and its 

 history entirely changed. 



New Developments 



An instrument enabling all sorts of coloured designs 

 to be viewed immediately in any desired colour com- 

 bination, the chromoscope now enters an indefinitely 

 enlarged sphere of usefulness. It is called the " Im- 

 proved Chromoscope," and its province, far from being 

 hmited to three-colour photography, covers textile 

 printing, wallpaper printing, weaving, chromo-litho- 

 graphy, and numerous other manufacturing processes 

 which make use of coloured design. 



Before hinting at the possibilities in this field, we 

 must first describe certain modifications in construction 

 (apart from the celluloid mirrors) which now make it 

 so comprehensive an instrument. These can best be 

 understood by reference to Fig. 2, which shows a per- 

 spective view of a ten-picture instrument. 



It will be seen that the instrument is divided into 

 a number of compartments. Each compartment con- 

 tains (s) a lamp the height of which can be adjusted 

 so as to vary the brightness of the corresponding 

 image ; (d) a piece of ground glass to diffuse the light 



and to obtain even illumination of the positive : (n) 

 a slot in which a holder containing the positive can 

 be placed (a " filter " of any desired colour can be 

 placed between D and n). In addition, each of 

 the compartments on the right-hand side of the instru- 

 ment contains a celluloid mirror (c) inclined at 45 

 degrees to the horizontal, and (m) a horizontal silvered 

 mirror. 



Considering the compartment nearest to the ob- 

 server, it can be readily seen that the light passes 

 through the filter to the positive. It is then trans- 

 mitted through the celluloid mirror, reflected from the 



Fig. 2.— the improved chromoscope— opticai< system. 



silvered mirror, and finally reflected from the under- 

 side of the celluloid mirror to the eye-piece. The 

 optical paths by which the remainder of the positives 

 on the right-hand side are viewed can be traced in a 

 similar way, and it will be seen that if the vertical 

 distance between successive horizontal mirrors is half 

 the horizontal distance between the successive in- 

 clined mirrors, the conditions as to equality of optical 

 paths wDl be fulfilled. 



The arrangement on the left-hand side of the instru- 

 ment is slightly different, and the images are viewed 

 from the eye-piece by means of two vertical silvered 

 mirrors (not shown in Fig. 2), each making an angle 

 of 45 degrees with the end of the instrument. 



With this brief outline of the optical system, we 

 are now ready to see by what means the colours of the 

 combined parts of the picture are altered. Taking 

 the case of a calico print design, a separate drawing 

 or impression is first made of each separate colour 

 element. From these drawings, a set of lantern-slide 



