236 THE BOOK OF THE LANTERN. 



exposure and development being so controlled that the 

 resulting pictures were somewhat denser than would be 

 advisable for an ordinary lantern-slide. They exhibited in 

 miniature every detail to be found in the negatives to 

 which they owed their origin ; and, in more than one case, 

 an improvement was effected in the process of reduction, 

 for some of the negatives were yellowed in certain portions, 

 and would, therefore, print unequally. This was obviated 

 by shading during exposure. 



The positives, although measuring only 2 inches across, 

 were taken for convenience on the standard plates for 

 lantern pictures, 3 J by 3 J ; so that a broad margin of 

 clear glass remained all round them. This was covered 

 with black varnish, after which the glasses were fitted into 

 the usual grooved carriers employed in lantern work. 



The next thing was to arrange a proper focussing-screen 

 for the reception of the image. This took the form of a 

 sheet of glass, 16 by 13, covered on one side with white 

 paper. Temporary wooden clips, fastened to the wall at a 

 convenient height from the ground, held this papered glass 

 in position, and in such a way that it could be readily re- 

 moved and a sensitive plate put in its place. 



It is with regard to the sensitive plates that I must now 

 speak. I found that commercial plates of the size required, 

 16 by 13, were very expensive; if I remember rightly, some- 

 thing like .2 per dozen was the price quoted to me. This 

 was more than I cared to expend on mere experimental 

 work ; besides which, it goes against the grain to buy 

 plates when one has been in the habit for years of making 

 them of unsurpassed quality. I now bethought me that I 



