Report on the Lister Legacy. By E, J. Spitta. 147 



No. 1. — This is probably one of the earliest of Lister's complete 

 combinations. Of about l^-in. focal length, it shows but a poor 

 image. Although much time and trouble were spent in trying all 

 kinds of adjustment, the red and blue images seem quite distinct, 

 so much so that no adjustment will make any sensible change. 

 It is not at all unlikely^ — ^especially as all the components in these 

 combinations are set quite loosely in their cells — either that some 

 lens has been placed in situ by mistake, or that perhaps a lens 

 has been omitted. Alternatively it has been suggested that pos- 

 sibly Lister had some special object in making a lens of this nature, 

 so that by using monochromatic light of one or other colour, he 

 might possibly obtain a better performance. 



No. ;^. — Is a §-in. and shows a great advance. Although the 

 components are only mounted in cardboard, still, with care and 

 time, a position was found when this combination furnished quite 

 a good image, more especially in the preferred colour, which seems 

 to be the apple-green as selected for the most part by modern 

 artists in the present day. Of course the aperture had to be some- 

 what severely cut down. 



No. 3. — This is an objective of renown^ being — according to 

 the memorandum accompanying it — " Tulley's original f^ , with 

 glasses by Chevalier." Its performance is really very wonderful, 

 especially when consideration is allowed for the small range of 

 glasses of the period. Like others of the same date it requires 

 rather severe cutting down of aperture. 



No. Jf. — This is an objective of about l-m. focal length. 

 With careful adjustment throughout, a positively fine image is 

 presented when a medium aperture only is used. It is a monu- 

 inent to the ability of Lister. 



No. 3. — Of about IJ-in. focal length. This objective is spoiled 

 by the degeneration (it is presumed) of one of its components. It 

 is, however, another remarkable objective. If cut down severely 

 so as to stop out entirely the outer and the greater portion of the 

 intermediate zone, its performance is really good, but if the objec- 

 tive be used at its full aperture, the effects of " outward coma " 

 become very pronounced, and the image of any object is almost 

 entirely spoilt and blurred. It has seemed as if this was another 

 experiment : — To perfect the inner and intermediate zones at the 

 expense of the outer. 



The fifth row is of antiquarian interest only. It contains a 

 chip-box, within which are several lenses of different glass and 

 curvature. Adjacent to this are two optical lathe-chucks, separated 

 by one of Lister's " polishing sticks," which carries the observer 

 back many years to the workshop of this wonderful man. 



The last object in the row is placed there purely for general 

 interest, being, a peculiarly-shaped envelope- wrapper, bearing the 

 date 1844. 



