9° 



SCIENCE- G OSSIP. 



MICROSCOPY FOR BEGINNERS. 



By F. Shilllsgtox Scales, F.R.M.S. 

 {Continued from j). 61.) 



If the microscope requires adjustment, these 

 adjustments should be made with the utmost care. 

 Most microscopes by our best English makers have 

 the wearing parts sprung so that the adjustments 

 may be readily effected, but even then a little 

 attention to the tools with which the work is done 

 may be recommended. The screwdriver, for in- 

 stance, should be in good condition. 



It is well also to bear in mind that the lacquer 

 on the brass-work of the microscope, placed there 

 not so much for appearance as for the prevention 

 of oxidisation, is destroyed by alcohol. 



Finally, our advice to the beginner who may 

 wish to oblige a friend by lending him his micro- 

 scope is — don't ! 



It now only remains for us to add a few hints 

 on mounting, and these we shall endeavour to 

 make as simple and practical as possible. The 

 beginner must bear in mind that mounting for the 

 microscope has become quite an art, if not a 

 science, and the list of reagents, stains, and media 

 used for special purposes would be quite a for- 

 midable one. Fortunately the requirements of 

 beginners and amateurs, especially those for whom 

 we are now writing, are much more easily dealt 

 with, and we shall confine ourselves to the simplest 

 and most commonly used methods, trusting that 

 as knowledge grows and experience comes with it, 

 the beginner will learn more of such advanced 

 methods from works dealing with the subject. 



It is of course only with very low powers, and 

 when the nature of the investigation admits of it, 

 that an absolutely unprepared and unarranged 

 object can be examined. For this purpose a 

 pocket -lens is infinitely preferable to the compound 

 microscope with all its complications and refine- 

 ments. For examination with the latter instru- 

 ment even opaque objects require to be properly 

 displayed, whilst objects to be examined with 

 transmitted or direct light — that is, by means of 

 light that passes through the object — require very 

 careful preparation beforehand. 



Wooden slips and paper-covered slips are now 

 very rarely used, 3 inch x 1 inch glass slips being 

 now almost universal. These can be obtained from 

 any optician. They should, preferably, have ground 

 edges, and for general purposes should be of medium 

 thickness. They will cost from twopence to five- 

 pence per dozen, according to quality, or less for a 

 larger quantity. If any of them should be found 

 to have scratches or specks in the centre, they 

 should be put aside for making opaque mounts. 

 For exceptionally large mounts slips 3 inches x 1§ 

 inch can be obtained. The cover-glasses should 

 be circular, in thickness from - 006 inch to -008 

 inch, and might vary in size from f inch to f inch 

 diameter. It would be well to provide oneself with 

 a stock of -f-inck, f-inch. and ^-inch cover-glasses, 

 and to note their thickness at the time of purchase, 

 and, generally speaking, to adhere afterwards to 

 the same standard for ordinary work. High-power 

 work with objectives of very short focus may 

 require, thinner cover-glasses to be used. We would 

 also recommend the purchase of a dozen or so 

 slips with excavated cells of various sizes, i.e. with 

 concavities around in their centres. 



Before use, all slips and covers must be scrupu- 

 lously cleaned. It is generally sufficient to wash 

 them with hot water and soap or soda ; but for 

 special work more drastic measures may be neces- 

 sary. The writer generally uses a fairly strong 

 and hot solution of Hudson's Soap, with subsequent 

 careful rinsing and polishing with an old cambric 

 handkerchief. The great thing to be avoided is 

 any suspicion of grease, even from the fingers 

 themselves. Cover-glasses must be finally polished 

 with chamois leather, and as they are very thin 

 and of course easily broken, various contrivances 

 such as buff blocks are obtainable for the purpose. 

 With a little practice, however, it is quite easy to 

 hold half the cover-glass in a piece of chamois 

 leather between the finger and thumb, but not 

 edgeways, and to polish the other half, turning the 

 glass round meanwhile. 



We will first deal with the mounting of opaque 

 objects and of objects that can be mounted dry, 

 this process being comparatively simple. The 

 various apparatus, reagents, media, stains, etc., will 

 be mentioned as we proceed, and their uses will 

 then become apparent at the same time. Accord- 

 ingly we shall here require a turntable. This is a 

 circular brass plate about 3 J inches in diameter, 

 mounted so as to rotate upon a centre, the upper 

 surface of this plate having concentric rings en- 

 graved upon its surface. These latter serve as a 



guide in centering the slide upon the rotating 

 plate. There is also a pair of clips to hold the 

 slide in place. The turntable is mounted on a 

 wooden block or iron stand which serves as a sup- 

 port for the hand. The cost will be about six 

 shillings. We do not recommend the-" self-center- 

 ing " turntables. We shall also need two or more 

 good sable brushes, which are best and cheapest in 

 the long run. These should be about Jg- inch and 

 ^ inch in diameter, costing ninepence or one 

 shilling each. Also a pair of steel or brass forceps, 

 not too narrow, costing one shilling and sixpence, 

 a bottle of gold-size, a bottle of Brunswick Black, 

 and a bottle of gum arabic. All of these are 

 obtainable from the opticians. 



The usual plan with opaque objects is to place 

 a slide on the turntable, centre by means of the 

 concentric rin°;s. and then run a disk of Brunswick 



