lamp flame exactly in the optical axis I incline the mirror so as to 
illuminate one side of the field more than the other (the light 
being then very slightly oblique) ; with this illumination a g 
well marked angulatum is shown as above described, the beads 
looking like minute hemispherical rubies ; the oil lens does the 
same if possible even better than the Tolles, the slight obliquity 
of the light suiting the oil lens better than when perfectly central, 
ut my Zeiss water immersion 1th and ;;th with same illumination 
only show the markings as black or brown dots, which appear 
almost flat like ink dots on paper, the ;,th and the oil lens showing 
them in unmistakeable relief. In working distance the oil lens 
has the best of the ;1;th as it works when in focus at about twice 
the distance of the latter; this very ample working distance is 
however in the case of the oil lens rather a disadvantage, as it is 
advantage the oil lens possesses over all other igh power lenses, 
is in inks requiring any correction for varying thickness of cover— 
this saves the observer a great deal of trouble. The Tolles oth i is 
very sensitive to its collar correction either dry or immersion, 
sa very decided ‘‘ best point ” with any given co 
Mr. Tolles has lately constructed a th which works ret ways 
iz. dry immersion with water, glycerine, or - 
In ordering mine I asked him to combine in as high a degree as 
_ possible resolving power with good central —_ i fair 
working distance and good performance wh cused dry, eerie I 
struction, modus eperetidiand | teiecantiaaaianl ‘Iluminator 
styled “ Tolles’s Semi-cylinder or Traverse Lens,” which is stated 
to be superior to Wenham’s Reflex for ultra — iljaminalee® 
asit gives illumination at any angle of incidence and res the 
—— at same time up to nearly 90° with the opie axis ‘a the 
CesT ina ahinies’ the information from Mr. Tolles I will 
acquaint the microscopists of our Society with the particulars ; 
ee nae. to be able to sho w this 7 
