47 
Glycerine, from its well-known preservative qualities, had been 
recommended as a medium; one caution, though, must be borne in 
mind : substances containing lime would be spoilt, as had been pointed 
out by Dr. Carpenter, who, employing glycerine to preserve penta- 
crinoid larvee of Comiatula, found that the calcareous skeletons were 
dissolved and the specimens spoilt. 
As a preservative medium, glycerine could be used alone, diluted 
with two parts of camphor water, with equal parts of gum arabic and 
water, and a small quantity of arsenious or carbolic acid ; or, what he 
had found worked admirably with many objects, glycerine jelly. 
The manuals on the microscope gave instructions how to prepare 
glycerine jelly ; but, as it could be purchased ready prepared,—and 
a small bottle would last years,—he would advise those who wished 
to try it to obtain either Rimmington’s or Aylward’s, both of which 
he had tried and liked. The former contained creosote, itself a good 
preservative, while the latter liquefied more readily, sometimes an 
‘advantage. = 
‘ 
For some delicate preparations he had found either could be 
- diluted with water. He had also tried the glycerine jelly, sold by the 
chemists for chapped hands ; but this required to be filtered before 
being used. ; 
Whichever form was employed, the gentle heat of a fire, lamp, or, 
best of all, of warm water, was required to liquefy the jelly, which 
could be applied in different ways. One method was to place a drop 
on each of several slides and let them cool ; then gently warming them 
the film at the top could be removed, thus carrying away air bubbles, 
or, while warm, the object could be immersed in the drop of jelly ; or 
the object might be placed on the slide, and as much of the moisture 
as possible being removed by blotting paper, the jelly might be 
dropped on it or placed by it, to run in of its own accord. 
The covering glass, previously warmed (best by dipping in warm 
-water), might be dropped on and gently pressed down and allowed to 
cool, when the superfluous jelly being cleared away, a ring of varnish 
could be run round, and the slide would be ready for the cabinet. It 
should be mentioned that the objects to be mounted should previously 
have been placed in water or diluted glycerine. 
One caution should be observed, viz., slide, jelly, covering glass; 
