MEMORANDA. 301 
nition when behind the slide. Over the prism in the camera 
lucida, the image of many objects appeared very strongly ; 
the pencil indistinct. The more or less translucent structures, 
as the feet and claws of Acari, had considerable boldness, 
and the foreshortening in the claws was more marked. Pos- 
sibly many of these variations may be due to the nature of 
the glass employed in the slide and objective, also of the 
medium in which the object was mounted, and might there- 
fore relate to these as well as to the objects themselves. 
Having much used sunlight concentrated by a prism and 
condenser in photomicrography, I consider the use of coloured 
glasses over the eye-piece with sunlight will render service in 
cases of doubtful structure. Sunlight with the parabola was 
employed by the Rev. Mr. Osborne in his examination of 
Closterium Lunula, ‘Mic. Journ.” No. VIII. Mr. Jabez 
Hogg, in the third edition of his work on the ‘ Use of the 
Microscope,’ says in examining the same object: “ Strong 
daylight should be transmitted ‘through coloured glasses pro- 
posed by Mr. Rainey, and adapted to ‘inch condenser, using 
4 objective.” I expect an equal if not a better effect would be 
found by using sunlight and coloured glasses over the eye- 
piece, as suggested by Mr. Wenham. I was not able to suc- 
cessfully use the parabola for producing photograph nega- 
tives.—R. Mappox. 
Method of Dry-mounting Entomological and other Objects.— 
Have ready a number of rings punched from thin gutta 
percha, supported on lead, folded in thin paper, to prevent 
“jagged” edges. Place the specimen on the slide, then the 
ring, the specimen being in the centre; then place a round 
cover on the ring, taking care to centre it to the round 
opening. Steady the cover by means of a needle, and apply 
a gentle heat beneath the slide. The gutta percha will be- 
come transparent, and a gentle circular pressure applied by 
the needle will cause both glasses to adhere. Allow the 
slide to cool, and afterwards remove the superfluous gutta 
percha with a penknife. The edge of the cover must then 
be cemented with varnish, applied in very small quantity at 
first. A second coating will complete the preparation.— 
THomas SHarMan Raxtpu, Melbourne, Australia. 
