146 Transactions of the Society. 



siderable historic value, and indeed forms such a valuable item in 

 the Society's Museum, that I have arranged it in a glass case so that 

 it can be viewed at any time. The individual objects are fixed 

 i% situ by pins inserted into the cork floor of the case — by which 

 means any article can be readily removed, and as easily replaced. 

 In most instances written details are supplied, probably in the 

 handwTiting of Lister himself, since they are cuttings from the 

 original papers, in which the objectives were wrapped. 



Descri'ption of the Contents of the Case. 



In the first row, commencing at the left hand, are five achro- 

 matic doublets, evidently of an experimental nature, being made of 

 different glasses and various curves. There is but little doubt that 

 all these doublets were made by Lister himself. Following them 

 are three plano-concave lenses, their wrapper being labelled "Lenses 

 of light flint, by Tulley ;" next to w^hich is shown a 1 J -inch doublet 

 by Chevalier, upon the wrapper of which appears the following, 

 " Original convexes to Tulley * 04." Completing the row is an 

 experimental concave (according to the wrapper) of "Faraday's 

 dense flint." As might be expected of this glass, it has degenerated 

 into almost an opaque mass. 



In the second row we find a doublet of " English and Swiss 

 plate," with the original memorandum by its side ; then follow six 

 early " fronts " and four triple combinations, all of which are 

 uncemented. A few simple lenses complete the row, and are 

 merely exhibited to show what an excellent polish Lister put upon 

 liis glasswork. 



In the third row, the first object of interest is what must be 

 taken as an experimental lens, details of which are given on the 

 wrapper attached thereto. Then come a series of specimens which, 

 it would appear, show the dawn of the single unachromatic hemi- 

 spherical front ; including one so small that it must have been 

 designed for some combination of very short focal length (e. g. ^-in., 

 J-in., or ^-in.). The construction of these lenses, small as of 

 necessity they must be, as well as the excellent polish they exhibit, 

 reflect no little credit upon the skill and workmanship possessed 

 by this marvellous man. A dark ground illuminator of the period 

 — strangely familiar to that made in the present day — some early 

 forms of sliding fronts to compensate for covered and uncovered 

 objects, or for differences in coverglass thicknesses, with some very 

 fine Lieberkiihns having a beautiful polish, complete this interest- 

 ing row. 



The fourtli row contains what is perhaps the most fascinating 

 of all the objects contained in the case, viz. : five combinations, 

 four of which it is almost certain were of Lister's own make. 



