380 FOREST ENTOMOLOGY. 



a full account of microscopical manipulation, a few general remarks, 

 together with some practical hints as regards special insects, may be 

 helpful to the young student. 



As regards the choice of a microscope, it is, of course, best to get 

 what is termed a good stand, as accessories can always he added. 

 The principal lenses required are the inch and quarter-inch objectives. 

 A power lower than the inch is very useful, but the greater portion 

 of practical work is always done with the inch objective. For the 

 examination of opaque objects a bull's-eye condensor is required. 



A small outfit of, say, a spirit-lamp, a pair of scissors, a small dis- 

 secting-knife, a few slips and cover-glasses, a bottle of balsam and 

 benzole, and a pair of forceps, are about all that are required for a 



start. 



Now let us prepare and mount a slide of some simple object. Take 

 a few slips and cover-glasses, and have them thoroughly cleaned : 

 then select a simple object, say a wing of a house-fly or the scales off 

 a butterfly's wing, gently warm the slip over the spirit-lamp (this is 

 not always done even by experienced workers), place the object in 

 the centre of the slip, drop a little balsam on the object, and with the 

 forceps lift a well-cleaned cover-glass and let it just "feel" the flame 

 of the spirit-lamp, so that any natural moisture may be removed, and let 

 it fall with its own weight on to the balsam on the slip, gently press 

 it, and keep it in position with a clip, lay it aside for a short time, 

 and the operation is completed, you have a mounted slide. Great 

 care should be taken to prevent air-bubbles, as they are the deadly 

 enemy of mounts. Such is the simple method of mounting viz., 

 to fasten the object between two glasses with Canada balsam, as 

 this resinous substance is highly refractive, and brings out the details 

 of structure. 



It would, of course, be well for the young student in a rural dis- 

 trict to get assistance from a naturalist friend in mounting, &c. A 

 good useful microscope and simple outfit cost about 8. 



In setting the insects hatching out from oak galls, the following 

 methods, either for microscopic slides or cabinet specimens, may be 

 adopted. First of all, get the insects separated from the galls by the 

 usual method of stupefying by chloroform. When under the influ-. 

 ence of the anaesthetic, place them in a clean empty box with a glass- 

 covered top, and when they revive and become active in the box, 

 " tap " them rapidly into a saucer containing boiling-water. When they 



