:g34 THE NATURALIST. 



the other parts to be used to their full advantage — hence first-class 

 workmanship is most desirable, nevertheless, where this cannot be paid 

 for, trouble and extra time can often make a less perfect, and more 

 cheaply made stand, do nearly all the work of the most costly. 



Next, the "object glasses" — these are far the most important of all; 

 in microscopic parts nothing will make up for bad object glasses, and 

 these involve the largest outlay, but then they can be bought one by 

 one, so that by this means they can be had in time, by any one who is 

 disposed to follow out this study. But I am happy to say that lately 

 cheap sets of object glasses have been brought out, I believe for about 25s. 

 each, (for the lower powers) which really are almost good enough for any 

 purpose, so that object glasses may be said to be within the reach of 

 everybody, and for a beginner will answer almost as well as the very best. 

 With these cheap object glasses there is a cheap Binocular* stand, so 

 that the instrument, which can be used as a Binocular, (then by simply 

 sliding out the prism as a " Monocular,") with two object glasses, case, 

 condenser, and I think two or three smaller etcs., can be had for about 

 £10 10s. Od. I doubt whether a better instrument than this can be had 

 for the money ; several of my friends have had this instrument and are 

 perfectly satisfied with it. Then we come to the " eye pieces," these are 

 more easily to be had than " object glasses." The relationship existing 

 between the " object glasses " and " eye pieces " is simply this, the object 

 glasses have a certain magnifying power, this is again magnified by the 

 eye pieces — for example, let us say the object glass magnifies a certain 

 object 50 diameters, this image is thrown on to the field glass (in the eye 

 piece), where, we will suppose again, it is magnified 10 times ; — the total 

 magnifying power will be seen to be ten times 50, or 500 diameters. All 

 this may appear very puzzling to a young beginner, but one thing soon 

 follows another, and there is so much to afi'ord pleasure in the very first 



* The Binocular arrangement has two bodies, and two eye pieces, so that both 

 eyes are used when an object is being examined; this, in my opinion, is not yet 

 sufficiently valued by most microscopists ; I believe it will be found greatly to preserve 

 the eyes from injury, as well as allowing the observer more comfort during his 

 investigations, while the objects are seen more perfectly, i. e. they are seen under the 

 microscope as we see objects by unaided vision. Most persons are unaware of the fact, 

 that with one eye we see objects very differently than we do with two, — to prove this, 

 let a person place himself at a given distance, and closely watch a certain object, using 

 one eye only ; after having fixed the image in the mind as it then appears, at once let 

 him open the other eye, and the difference is at once apparent — let this act be repeated 

 several times, and it will rather surprise those who have never tried it. 



