HARDWICKE'S SCIENCE-GOSSIP. 



55 



Soak i oz.* best amber gelatine (as sold by the 

 chemist or grocer) in loz. distilled water; when it 

 has absorbed all the water, put it in a Florence flask 

 with 50 grains of powdered chloride of barium, 

 warm it in a water-bath and agitate till the barium 

 salt is dissolved. Allow it to cool below blood-heat, 

 and while still fluid add 1 oz. Price's glycerine and 

 a teaspoonful of white of egg ; shake until well 

 mixed, replace in the water-bath, and boil at full 

 speed until the albumen compleielp separates from 

 the jelly in the form of a single lump. Now filter 

 through well- washed fine flannel, and it should be 

 as clear as crystal ; but if through mismanagement 

 it be a little cloudy, filter it again, this second time 

 using filter-paper, and placing the funnel with the 

 jelly, &c., in a cool oren. During the coagulation of 

 the albumen, the jelly must on no account be stirred. 

 It is well to beat up the white of egg before use, 

 lest it should be stringy. In lieu of a water-bath a 

 saucepan may be used ; and a little salt thrown into 

 the water causes it to boil at a greater heat. 



The jelly made after this recipe is of the proper 

 consistency for entomological objects ; but for deli- 

 cate vegetable structures it should be softened by 

 adding to it a third of its volume of a mixture of 

 equal parts of glycerine and distilled water. 

 :^ Put the jelly into test-tubes i inch.in diameter, and 

 ■when you wish to mount a slide, warm the upper 

 part of the tul)e; in this way you can pour out any 

 quantity free from bubbles. It is perhaps well to 

 put a trace of varnish or some essential oil on the 

 corks, lest they should get mouldy. The chloride of 

 barium prevents fungi in the jelly : this is the best 

 preservative we know of, but something is absolutely 

 necessary. By all means avoid putting alcohol, 

 creasote, &c., in the jelly, as they dissolve varnishes, 

 and also spoil the colour of some objects. 



TVe will now proceed to the mounting operations, 

 and will take an insect for the first example. — 

 Having dissected the fly, or whatever it may be, put 

 the transparent parts (wings, and perhaps halteres) 

 in a little folded piece of cream-laid note-paper with 

 a drop or two of glycerine, and torite the name on the 

 outside, or you are sure to forget the particular 

 insect which they belong to. Soak the opaque parts 

 in caustic potash solution as usual ; boil them once 

 or if necessary twice, in distilled water, using fresh 

 water each time. The objects may now be mounted 

 at once, or kept in glycerine till wanted, and at the 

 time of mounting rinsed in water to remove the 

 glycerine. To mount them, arrange them neatly 

 on a slide, suck away the superfluous moisture 

 through a fine-pointed glass tube ; lay on the thin 

 glass cover, and secure with a strong brass clip, or, 

 if the cover be large, use two or more clips. Now 

 drop a little liquefied jelly round the edge of the 

 cover : it will run under, and look too full of bubbles 

 to be good for anything, but that is no matter ; just 

 warm it over a small lamp-flame until it boils and 



the air is driven out, and when the slide is quite 

 cold it will be free from bubbles, or any bubble left 

 near the edge will disappear in a short time. The 

 jelly must actually boil, hut 7io more. A great many 

 bubbles will be given off before it really boils, but 

 when the heat reaches a certain point the jelly will 

 burst out from under the cover with a slight noise, 

 and the slide should be taken away from the flame 

 immediately. Every now and again you will get a 

 slide so full of bubbles that they will take a week 

 to go away, and perhaps even a second boiling will 

 be necessary; but this is very seldom. : After leaving 

 the slide for a few hours for the jelly to set, clean it 

 with a tooth-brush and cold water, carefully wipe 

 it dry, and cement at once with gold size, of which 

 two or three coats should be applied. India-rubber 

 varnish is perhaps better than gold size for the first 

 coat, for the latter cement sometimes runs in and 

 spoils the object ; but if it be only laid ,on thin 

 enough, this will not often happen. Any varnish 

 containing alcohol is worse than useless, because it. 

 will mix with the jelly. 



The above plan may be applied to palates of' 

 moUusks and all animal objects that are not injured 

 by heat. Injections of course would be spoilt by 

 it. Many vegetable objects, such as wood-sections, 

 tough cuticles, and others of a like nature, may be- 

 mounted in the same way as an insect, but delicate 

 vegetable structures and objects in cells must be 

 mounted as follows. Air may be expelled by boiling 

 in water, or, in extreme cases, in alcohol, and after- 

 wards washing in water. If that which you wish to 

 mount be such as an alga, you cannot boil it at all, 

 but must merely wash it in clean water, and absorb 

 superfluous moisture with a glass jet. 



To proceed. — Drop a little jelly on the centre of 

 a slide, warm it slightly, but not above blood-heat ;. 

 place the object in the centre ; move it gently with 

 a needle to let the jelly penetrate it ; lay the cover 

 on quite horizontally — and not one side first, as 

 usually recommended, — and when cold clean and 

 varnish. Cells are not often required : only for very 

 thick objects and certain algpe, &c. They may be 

 made of glass, tin, or vulcanite, and should be stuck 

 with marine glue, which is about the only trust- 

 worthy cement, or they may be of rings of gold size 

 heated strongly until of a brownish hue. When 

 mounting in a cell, the boiling method is imprac- 

 ticable. 



If you wish to use balsam in the same way, 

 after the objects are boiled in water rinse them in 

 methylated spirit, and soak for a time in absolute 

 alcohol ; transfer to oil of cloves or carbolic acid 

 (oil of cloves is the better of the two) ; then lay 

 them on the slide, and mount and boil as above. 



For Dammar.— On taking the objects from water, 

 arrange them on a slide with cover and clip, and 

 set it aside till dry ; then allow a drop of benzole 

 to run under the cover ; about one minute afterwards 



